LIBRARY 


UNIVERSITY  OF  CALIFORNIA. 


GIFT    OF 


Class 


THnt\>er0it£  of 

FOUNDED  BY  JOHN  D.  ROCKEFELLER 


THE  PLEISTOCENE  DEPOSITS  IN 
WARREN  COUNTY,  IOWA 


A  DISSERTATION 

SUBMITTED    TO    THE    FACULTY    OF    THE    OGDEN    GRADUATE    SCHOOL 

OF    SCIENCE    IN    CANDIDACY    FOR    THE    DEGREE 

OF  DOCTOR  OF  PHILOSOPHY 

(DEPARTMENT  OF  GEOLOGY) 


BY 


JOHN  LITTLEFIELD  TILTON 


THE  UNIVERSITY  OF  CHICAGO  PRESS 
CHICAGO,  ILLINOIS 


THE  UNIVERSITY  OF  CHICAGO  PRESS 
CHICAGO,  ILLINOIS 

Bgente 
THE  BAKER  &  TAYLOR  COMPANY 

NEW  YORK 

CAMBRIDGE  UNIVERSITY  PRESS 

LONDON  AND  EDINBURGH 


ZTbe  Tnniversttg  ot  Cbtcaao 

FOUNDED  BY  JOHN  D.  ROCKEFELLER 


THE  PLEISTOCENE  DEPOSITS  IN 
WARREN  COUNTY,  IOWA 


A  DISSERTATION 

SUBMITTED    TO    THE    FACULTY    OF    THE    OGDEN    GRADUATE    SCHOOL 

OF    SCIENCE    IN    CANDIDACY    FOR    THE    DEGREE 

OF  DOCTOR  OF  PHILOSOPHY 


(DEPARTMENT  OF  GEOLOGY) 


BY 
JOHN  LITTLEFIELD  TILTON 


THE  UNIVERSITY  OF  CHICAGO  PRESS 
CHICAGO,  ILLINOIS 


TU 


EARTH 

SCIENCES 

LIBRARY 


COPYRIGHT  1911  BY 
THE  UNIVERSITY  OF  CHICAGO 


All  Rights  Reserved 


Published  January  191 1 


Composed  and  Printed  By 

The  University  of  Chicago  Press 

Chicago,  Illinois,  U.S.A. 


• 


CONTENTS 

PAGE 

INTRODUCTION        ..........  i 

Location          ....                                                        .  i 

Previous  and  Recent  Work        ...  i 

Acknowledgments                                        -  .  3 

THE  PLEISTOCENE  DEPOSITS  CONSIDERED  AS  A  WHOLE,  AND  THE  PRE- 

GLACIAL  SURFACE          .....         ...         .  4 

Thickness  of  the  Pleistocene  Deposits          .....  4 

Maximum  Thickness  of  the  Drift  Compared  with  the  Present  Relief  4 

The  Preglacial  Drainage    .                  -.         .  v    -  .         .                   .  5 

THE  RECORD  OF  THE  SIMPSON  COLLEGE  WELL  7 

The  Record  Briefly  Stated        .         .  7 

The  Record  Stated  in  Detail      .         .  7 

The  Post-Kansan  Surface  Deposits       .  7 

The  Sub-loessial  Sand  8 

The  Kansan  Drift      .  8 

The  Aftonian  Deposits        .                                               •  9 

Analysis  of  Gravel        .  10 

Carboniferous    .         .  .  .11 

The  Water       .  n 

Discussion       .  ....  .11 

THE  SUB- AFTONIAN  DRIFT       .                                    .  13 
The  Name       .......                            .13 

The  Sub- Aftonian  Drift  in  General     .          .          .          .          .          .  13 

The   Distribution   and   Relation   of   the   Sub-Aftonian   Drift   in 

Warren  County      .......  15 

Gravel  from  Sub-Aftonian  Drift,  in  Wells  .         .         .         .  17 

Gravel  from  Sub-Aftonian  Drift,  in  Outcrops       .         .  18 

On  the  Thickness  of  the  Sub-Aftonian  Now  Remaining  18 

THE  AFTONIAN  INTERGLACIAL  DEPOSITS   ...  20 

The  Name       .......  20 

The  General  Character  of  the  Aftonian  Deposits  20 

Various  Exposures  of  the  Aftonian      .  21 

Fossils  from  the  Aftonian           .          .                   .                   .  26 

The  Source  of  the  Material        .                   .                   ...  27 

Aftonian  Relief  28 


218000 


IV  CONTENTS 

PAGE 

THE  KANSAN  DRIFT       .                  .  30 
The  Name       ......                   .                   .30 

The  General  Character  of  the  Kansan  Drift         ....  30 

The  Kansan  Drift  Contrasted  with  the  Sub-Aftonian  Drift  in  Com- 
position and  Topography 33 

The  Kansan  Drift  Contrasted  with  the  Wisconsin  Drift  in  Com- 
position and  Topography          ....  34 
The  Distribution  and  Thickness  of  the  Kansan  Drift    .  35 

THE  POST-KANSAN  DEPOSITS  ....  .  37 

The  Post-Kansan  Deposits  Found  in  the  Simpson  College  Well, 

and  the  Relation  of  Such  Deposits  throughout  the  County  37 
Cause  of  Renewed  Erosion  along  the  Hillsides  .  .  .  .38 
Analyses — Discussion  .  .  .  .  .  ...  .40 

SUMMARY  or  TOPOGRAPHIC  HISTORY  ,   .         .         .         .         .42 


INTRODUCTION 

LOCATION 

The  northern  boundary  of  Warren  County  lies  five  miles  south  of 
the  city  of  Des  Moines,  and  hence  five  miles  south  of  the  vanishing 
edge  of  the  Des  Moines  lobe  of  the  Wisconsin  drift  sheet,  from  which 
it  is  separated  by  the  Raccoon  and  Des  Moines  rivers.  These,  after 
their  union,  form  the  boundary  of  the  northeastern  part  of  the  county. 
The  five  hundred  and  seventy  and  one-half  square  miles  of  Warren 
County  thus  lie  in  that  broad  extent  of  southern  and  western  Iowa  where 
the  surface  drift  is  called  the  Kansan  drift.  The  problems  involved  are 
those  of  the  post-Kansan  surface  deposits,  the  Kansan  drift,1  the  Af tonian 
interglacial  deposits,  the  sub-Aftonian  drift,  the  preglacial  deposits  on 
Carboniferous  strata,  and  the  several  topographies  that  were  developed. 

PREVIOUS  AND  RECENT  WORK 

The  Carboniferous  strata  of  the  county  were  examined  in  1893-94 
and  described  (by  the  writer)  in  Vol.  V  of  the  Iowa  Geological  Survey. 
While  Vols.  I-VII  were  in  course  of  preparation  it  was  generally  sup- 
posed that  there  were  but  three  different  drift  sheets  in  Iowa  and  that 
those  described  by  McGee  in  his  "Pleistocene  History  of  Northeastern 
Iowa"2  were  the  drift  sheets  present  in  southern  Iowa.  The  differences 
found  were  considered  local  variations.  The  early  volumes  of  the  Iowa 
Geological  Survey  contain  many  interesting  facts  and  general  descrip- 
tions which  can  now  easily  be  read  in  the  present  terms  of  Pleistocene 
classification.  The  accumulation  of  these  facts  led  first  to  a  compari- 
son with  the  corresponding  relations  in  Wisconsin,  especially  through 
the  kindness  of  Professors  T.  C.  Chamberlin  and  R.  D.  Salisbury,3  and 
then  in  southeastern  Iowa,  through  the  kindness  of  Mr.  Frank  Leverett 
who,  in  his  study  of  the  "Illinois  Glacial  Lobe,"4  had  crossed  over  from 
Illinois  into  southeastern  Iowa.  H.  F.  Bain  then  worked  out  the  general 
relations  of  the  drift  sheets  and  published  his  paper  as  a  part  of  Vol.  VI,5 

1  For  map  of  the  drift  sheets  of  Iowa  see  Iowa  Geological  Survey,  Vol.  XIV,  Plate 
III. 

2  Eleventh  Annual  Report,  U.S.G.S. 

3  Iowa  Geological  Survey,  Vol.  VI,  p.  434;  Vol.  VII,  pp.  19-20. 
<  Monograph  U.S.G.S.,  Vol.  XXXVIII. 

s  In  Vol.  VI,  Iowa  Geological  Survey,  pp.  434-37,  446,  and  463-67,  Bain  gives  an 
excellent  summary  of  the  development  of  the  knowledge  of  the  drift  sheets  of  Iowa 
up  to  that  time  and  references  to  reports  on  previous  work. 


PLEISTOCENE   DEPOSITS   IN   WARREN   COUNTY,    IOWA 


Iowa  Geological  Survey,  which  was  followed  by  a  general  classification 
of  the  Pleistocene  deposits  by  Professor  Samuel  Calvin  in  the  Adminis- 
trative Report  of  Vol.  VII.  Since  that  time  (December,  1896)  the 
details  of  county  work  have  brought  to  light  evidence  of  a  sub-Aftonian 
drift,  a  still  older  drift  than  McGee  recognized  as  his  oldest  drift  de- 
scribed in  his  " Pleistocene  History  of  Northeastern  Iowa."1 

In  the  Bulletin  of  the  Geological  Society  of  America,  March,  1909, 
Professor  Calvin  discusses  the  "Recent  Phase  of  the  Pleistocene  Prob- 
lem in  Iowa."  In  a  December  bulletin  of  the  same  society  Professor 
Shimek  describes  the  "Aftonian  Sands  and  Gravels  in  Western  Iowa," 

WARREN  COUNTY 


R.  XXV  W. 

R.  XXIV  W. 

R.  XXIII  W. 

R.  XXII  W. 

Linn 

Greenfield 

Allen 

Richland 

Tp.  77  N. 

Jefferson 

Lincoln  and 
Greenfield 

Lincoln  and 
Palmyra 

Union 

Tp.  76  N. 

Jackson 

White  Oak 

Otter 

Belmont 

Tp.  75  N. 

Virginia 

Squaw 

Liberty 

White  Breast 

Tp.  74  N. 

Diagram  stating  the  combination  of  names  used  to  designate  the  various  govern- 
ment townships. 

and  in  an  October  bulletin  Professor  Calvin  describes  the  remarkable 
mammalian  fauna2  which  had  been  unearthed  by  Professor  Shimek  in 
his  work  upon  the  Aftonian  deposits  along  the  Missouri  River  and 
tributaries  in  western  Iowa. 

The  gradual  accumulation  of  data  in  different  parts  of  the  state 
made  it  seem  advisable  to  ascertain  if  possible  whether  the  drift  which 
had  been  called  Kansan  in  Warren  County  presented  evidence  of  a  divi- 
sion into  two  drift  sheets.  The  field  work  which  was  necessary  to  this 
paper  occupied  the  summers  of  1904  and  1905.  During  that  time  eight 
hundred  and  sixty-five  well  records  were  obtained,  and  further  observa- 
tions were  made  on  innumerable  exposures  by  the  roadside  and  in 
ravines.  Fortunately,  at  the  very  close  of  the  field  work,  a  well  one 
hundred  and  twelve  feet  deep  was  bored  on  the  campus  at  Simpson 

1  Eleventh  Annual  Report,  U.S.G.S. 

3  S.  Calvin,  "Aftonian  Mammalian  Fauna,"  Bulletin  of  the  Geological  Society  of 
America,  Vol.  XX,  pp.  341-56. 


INTRODUCTION  3 

College  that  afforded  the  most  complete  section  through  the  Pleistocene 
deposits  that  it  had  been  possible  to  obtain.  This  record  is  presented  in 
detail  and  the  data  from  other  parts  of  the  county  are  compared  with  it. 
In  the  following  pages  it  is  frequently  desirable  to  refer  to  the  various 
townships  by  name  instead  of  by  number.  In  so  doing  the  irregularity 
of  the  township  lines  in  the  central  and  northeastern  parts  of  the  county 
make  it  desirable  to  combine  names  as  given  in  the  accompanying 
diagram. 

ACKNOWLEDGMENTS 

I  am  especially  grateful  to  Professors  T.  C.  Chamberlin,  R.  D.  Salis- 
bury, and  Samuel  Calvin  for  careful  criticism  of  both  an  earlier  report 
and  the  present  paper.  While  none  of  these  gentlemen  are  responsible 
for  any  defects  that  may  appear,  much  of  what  may  be  of  merit  is  due 
to  their  keen  and  kindly  criticism. 

To  Mr.  J.  C.  Nash,  Mr.  John  Tucker,  and  Mr.  N.  I.  Bowen  (who 
are  in  the  well  business)  I  am  indebted  for  the  records  which  they  have 
given  me  of  the  depth  of  wells  and  the  general  character  of  material 
found  in  the  various  parts  of  the  county,  and  also  for  their  kindness  and 
aid  on  a  number  of  trips  on  which  I  have  been  with  them  to  examine  the 
material  as  it  was  removed  from  the  ground.  I  am  also  indebted  to  the 
farmers  throughout  the  county  for  their  uniform  courtesy  and  aid. 
To  Professor  W.  B.  Read  I  am  indebted  for  a  series  of  levels  extending 
sixteen  miles  north  and  south  through  Indianola,  obtained  at  my  request 
by  a  class  in  surveying  under  his  direction. 


THE  PLEISTOCENE  DEPOSITS  CONSIDERED  AS  A  WHOLE, 
AND  THE  PREGLACIAL  SURFACE 

THICKNESS   OF  THE  PLEISTOCENE  DEPOSITS 

The  Pleistocene  deposits  as  a  whole,  together  with  the  recent  and 
subglacial  sands  and  clays,  have  a  maximum  thickness  of  two  hundred 
and  fifty-five  feet,  a  minimum  of  zero  feet,  and  an  average  of  forty-nine 
and  eight  one-hundredths  feet,  in  the  three  hundred  and  sixteen  wells 
which  extend  either  definitely  through  the  deposits  or  into  thin  deposits 
resting  on  the  Carboniferous.  Of  these  three  hundred  and  sixteen 
wells,  eight  reach  the  Carboniferous  at  depths  of  not  over  six  feet,  and 
forty-two  at  depths  of  one  hundred  feet  or  more.  To  this  latter  number 
should  be  added  four  which  are  one  hundred  or  more  feet  deep  but  do 
not  reach  the  bottom  of  the  drift,  and  seven  others  which  may  possibly 
extend  through  the  drift.  There  are  also  three  others  that  reach  the 
Carboniferous  but  at  depths  not  ascertainable,  two  of  which  should  be 
included  with  those  indicating  a  depth  of  one  hundred  feet  or  more  to 
the  bottom  of  the  drift,  making  fifty-five  wells  in  all. 

On  comparing  the  different  data  it  is  noted  that  the  tops  of  nearly  all 
of  the  wells  where  the  drift  approaches  a  hundred  feet  in  thickness  are 
at  or  near  the  level  of  the  upland.  The  tops  of  wells  revealing  very  thin 
Pleistocene  deposits  are  in  various  relations  to  the  upland,  four  occurring 
on  the  upland,  four  on  the  lowland,  and  the  others  at  intermediate  levels; 
and  all  are  where  outcrops  of  the  Carboniferous  are  most  numerous. 
Nearly  all  of  such  wells  and  outcrops  lie  near  or  northeast  of  a  diagonal 
line  extending  from  the  northwest  to  the  southeast  corner  of  the  county. 

MAXIMUM   THICKNESS   OF   DRIFT   COMPARED   WITH   THE   PRESENT   RELIEF 

According  to  the  following  table  in  which  a  comparison  is  possible 
between  the  maximum  thickness  of  the  Pleistocene  deposits  and  the 
present  relief,  the  maximum  thickness  of  the  deposits  exceeds  the  present 
relief  in  Jefferson  and  Virginia  townships  and  about  equals  the  present 
relief  in  Linn,  Greenfield,  and  Jackson  townships.  In  all  the  other 
townships  the  present  maximum  relief  exceeds  the  present  thickness  of 
the  drift.1 

1  The  statement  of  present  relief  is  based  in  part  on  the  Des  Moines  and  Milo 
topographic  sheets,  photographs  of  which  have  been  received  in  season  to  be  of  use  in 
revising  this  manuscript.  Other  data  used  in  the  estimates  may  be  found  in  the 
"Geology  of  Warren  County,"  Iowa  Geological  Survey,  Vol.  V,  pp.  315-17- 

4 


PLEISTOCENE   DEPOSITS   AND   PREGLACIAL   SURFACE 


Township 

Present  Maximum 
Thickness  of  Drift 

Present  Relief 

Linn  

142  ft 

130  ft 

Greenfield 

T  OC 

Allen   . 

IIC 

Richland 

68 

1  86 

Jefferson  

1  80 

140 

Lincoln  and  Greenfield  
Lincoln  and  Palmyra  
Union  

H5 
118 

-2Q 

163 
163 

I4.O 

Jackson 

167 

White  Oak 

I  ^O 

1  80 

Otter 

4.O 

1  80 

Belmont 

A-2 

IOO 

Virginia 

2  c  e 

2OA 

Squaw  . 

T\ 

I  37 

Liberty   .    . 

ICK 

I  37 

White  Breast  . 

?2 

IQO 

Average  

112 

l62 

THE   PREGLACIAL  DRAINAGE 

Attempts  to  determine  the  direction  of  the  preglacial  drainage  are 
not  satisfactory,  partly  because  of  uncertainty  as  to  whether  the  lowest 
level  of  the  Carboniferous  surface  beneath  the  sub-Aftonian  as  given 
by  the  well  records  marks  the  lowest  parts  of  the  preglacial  valleys. 
The  uncertainty  as  to  exact  level  that  existed  all  through  the  field 
work  for  lack  of  a  topographic  map,  making  it  necessary  to  assume  levels 
for  the  present  upland  based  on  a  few  railroad  levels  and  determina- 
tions with  a  barometer,  is  now  partly  relieved  by  photographs  of  the 
completed  Des  Moines  sheet  and  the  partially  completed  Milo  sheet 
which  give  levels  for  the  extreme  northern  and  eastern  parts  of  the 
county.  Estimates  of  the  lowest  portions  of  the  upper  surface  of  the 
Carboniferous  where  found  beneath  glacial  deposits  are  as  follows: 


Township 

Lowest  Portions  of  the 
Upper  Surface  of  the 
Carboniferous  Found 
Beneath  Glacial  Deposits 

Present  Highest  Parts  of 
the  Upper  Surface  of 
the  Carboniferous 

Greenfield  

815  ft.  AT 

900  ft.  A  T 

Allen  

8=58 

Jefferson  

870 

Jefferson  

OOI 

Jefferson  

855 

Lincoln  and  Greenfield  
Lincoln  and  Greenfield  

925 

QIC 

Virginia 

I  O^O 

Virginia 

I  O2O 

I  O3O 

Liberty.  .  .  . 

807 

... 

6  PLEISTOCENE   DEPOSITS   IN   WARREN   COUNTY,    IOWA 

Here  the  general  slope  of  the  lowest  portions  of  the  upper  surface 
is  toward  the  north,  but  the  data  are  not  sufficiently  extensive  to  make 
a  determination  of  the  average  gradient  possible.  The  difference 
between  the  lowest  level  in  Greenfield  Township  (815  ft.  A.T.)  and  the 
highest  level  of  the  Carboniferous  surface  at  the  present  time  (900  ft. 
A.T.)  gives  a  relief  of  85  feet,  which  is  less  than  the  true  preglacial 
relief  because  of  Aftonian  erosion  of  the  upper  surface  of  the  Carbon- 
iferous. (The  surface  of  the  Carboniferous  at  that  point  was  protected 
from  post-Kansan  erosion  by  the  Kansan  drift,  which  still  remains.) 

Further  evidence  with  reference  to  the  preglacial  surface  may  be  found 
in  the  regions  of  deepest  drift  bounded  partially  by  irregular  Carbonifer- 
ous outcrops.  These  heaviest  deposits  of  the  drift  make  it  evident  that 
from  the  southern  and  eastern  parts  of  Jackson  Township  a  large  val- 
ley extended  southeastward  across  Squaw  Township  and  northwest- 
ward across  Jefferson.  A  branch  of  this  valley  extended  eastward  from 
Jefferson  Township  to  Indianola,  and  another  northeastward  to  the 
southwest  corner  of  Greenfield  Township.  Another  valley  underlies 
the  central  part  of  Linn  Township,  from  which  there  is  an  extension 
southwest  and  northwest.  The  distribution  of  the  thick  drift  suggests 
an  outlet  to  the  northwest,  but  the  direction  of  the  preglacial  valleys 
suggests  an  outlet  more  to  the  north  through  Greenfield  Township. 

Where  the  surface  of  the  Carboniferous  is  penetrated  the  gradations 
due  to  weathering  are  frequently  evident  from  the  incoherent  upper 
portions  to  the  more  consolidated  portions  below.  The  records  of  wells 
that  penetrate  the  deeper-lying  portions  of  the  Carboniferous  surface 
generally  state  that  sand  is  found,  but  in  a  few  instances  old  soil  and 
fragments  of  wood.  Such  deposits  are  not  Aftonian  for  they  lie  below 
sub-Aftonian  drift,  and  at  levels  out  of  accord  with  Aftonian  drainage 
lines. 


THE  RECORD  OF  THE  SIMPSON  COLLEGE  WELL 

In  the  summer  of  1907  a  series  of  four  wells  was  sunk  within  a  radius 
of  fifteen  feet  on  the  campus  of  Simpson  College,  giving  the  best  record 
which  it  has  been  possible  to  obtain  in  the  county.  This  record, 
made  as  the  material  was  removed,  is  here  presented  in  detail.  It 
serves  as  a  typical  record  down  to  the  Aftonian,  beyond  which  the 
deposits  described  are  not  commonly  reported  within  the  county.  The 
surface  of  the  well  is  at  970  ft.  A.T. 

THE   RECORD  BRIEFLY   STATED 

2  ft.     Soil,  black  (loess  and  humus). 
28  ft.    Loess,  yellow  above,  blue  below;    then  blue  clay  (gumbo,  a  modified 

loess);  then  a  grayish-blue  sandy  loess;  no  effervescence. 
2  ft.     Sand,  yellowish  and  gray.  Sub-loessial 

54  ft.  Clay,  with  pebbles,  bowlders,  and  lime  concretions;  yellowish  brown 
for  one  foot,  then  grayish  blue -for  seventeen  feet,  then  bluish  black 
for  thirty-six  feet.  Kansan 

25  ft.    Deposit,  black,  with  old-soil  plains  and  minute  partings  of  vegeta- 
tion, but  no  wood,  and  almost  no  pebbles.  Aftonian 
i  ft.    Pebbles  from  sub-Aftonian.                                                        Aftonian 


112  ft.    (Ends  on  the  Carboniferous.)  Carboniferous 

THE  RECORD  STATED  IN  DETAIL 

The  Post-Kansan  Surface  Deposits 
2  ft.     Soil,  a  black  loam  (loess  and  humus). 

28  ft.  A  brownish  loam  for  ten  feet,  porous,  a  mixture  of  clay  and 
microscopic  particles  of  quartz,  streaked  with  brown  oxide  of 
iron  in  rootlike  tubes  and  with  very  thin  layers  of  a  dark-brown- 
ish sand;  entirely  free  from  pebbles.  At  thirteen  feet  from  the 
surface  the  deposit  is  less  clayey  than  above  and  contains  more 
numerous  streaks  of  a  brownish  sand.  Two  feet  deeper  (at 
15  ft.)  the  deposit  is  slightly  bluish;  then  for  three  feet  is  a  dense 
blue  clay  free  from  sand  and  impervious  to  water,  but  still  free 
from  effervescence  and  free  from  pebbles.  (The  ground-water, 
the  surface  of  which  was  encountered  at  eight  feet,  rests  on  the 
impervious  clay  at  this  level.)  For  the  next  eight  feet  (to  26 
ft.)  the  clay  is  of  a  light  grayish  blue,  still  free  from  pebbles 


8  PLEISTOCENE   DEPOSITS   IN  WARREN   COUNTY,    IOWA 

and  effervescence.  At  first  (at  21  ft.)  it  is  somewhat  more 
gritty  than  above  and  contains  traces  of  a  brown  oxide  of  iron. 
The  first  four  feet  of  the  eight  caved  badly,  large  water-soaked 
masses  (wet  from  below  upward)  scaling  in  vertical  sheets  from 
the  sides  of  the  well,  as  the  uppermost  phase  of  the  loess  does 
by  the  roadside. 

The  first  pebble,  encountered  at  a  depth  of  twenty-six  feet, 
was  a  small  angular  red  granite,  dimensions  i56  XTB  XyV  of  an 
inch.  In  the  next  two  feet  (to  28  ft.)  the  deposit  (the  lower 
loess)  contains  a  fine  sand  and  spherical  grains  of  quartz  ^  of 
an  inch  in  diameter.  The  remaining  four  feet  to  the  sand  (sub- 
loessial)  is  grayish  in  color  and  with  a  grayish  and  brown  sand 
through  it.  In  the  bottom  of  this  deposit  was  a  pebble  f  XI  X| 
of  an  inch,  and  grains  of  quartz  up  to  -J-  of  an  inch  in  diameter. 

The  Sub-loessial  Sand 

2  ft.  Sand,  pure,  brown  and  gray.  At  the  well  to  the  east  this  sand 
is  almost  wanting.  At  the  well  farthest  west  the  sand  is  nearly 
four  feet  thick.  At  the  intermediate  wells  it  is  about  two  feet 
thick,  the  bottom  of  the  sand  sloping  to  the  west. 

The  Kansan  Drift 

54  ft.  Directly  beneath  the  sub-loessial  sand  is  a  light  brownish-blue 
stiff  clay  in  which  the  first  concretion  of  calcium  carbonate 
was  found,  and  two  small  pebbles  of  greenstone,  then  a  bowlder 
too  large  to  get  into  the  auger,  and,  at  33  feet,  a  dark-blue  clay 
with  the  first  distinct  effervescence  of  the  clay  itself,  this  efferves- 
cence continuing  with  each  auger  full  for  fifty-three  feet  till  the 
bottom  of  the  Kansan  had  been  reached  at  a  depth  of  86  feet. 
Here  at  33  feet  were  also  found  a  rounded  quartz  and  a  sub- 
angular  limestone  pebble. 

From  33  feet  to  49  feet  the  clay  varied  from  a  brownish  clay 
to  a  light-bluish  clay  and  then  to  a  grayish  blue,  with  brown 
sand  and  gravel  scattered  through  it,  and  with  pebbles  and  bowl- 
ders. At  47  feet  the  surface  of  this  grayish-blue  clay  was  of  a 
darker  shade;  at  48  feet  there  were  patches  of  a  dark-blue  clay 
2X1 JX  i  inch  grading  outward  into  a  lighter  blue  clay,  thus 
forming  pieces  of  a  dark-blue  clay  surrounded  by  zones  of  the 
gray  clay  weathered  in  from  the  streaks  of  sand,  the  darker 
blue  clay  containing  pebbles  and  scattered  grains  of  sand,  thus 


RECORD  OF  SIMPSON  COLLEGE  WELL  9 

resembling  in  all  respects  except  color  the  grayish-blue  clay  and 
the  bluish-gray  clay  ab.ove.  In  the  next  foot  the  pieces  of  dark 
blue  were  larger,  the  gray  lying  in  distinct  planes  between  the 
masses  of  dark  blue. 

From  50  to  86  feet,  the  bottom  of  the  clay  that  effervesced, 
the  clay  was  bluish  black  and  dry  (the  unoxidized  and  unhy- 
drated  portion  of  the  Kansan),  with  a  fine  brown  sand  in  little 
pockets  half  an  inch  or  so  in  diameter  and  in  thin  irregular 
bands  similar  to  those  along  which  the  blue  in  the  upper  two  feet 
is  weathered  into  the  irregular  masses.  There  were  numerous 
pebbles,  lime  concretions,  and  fragments  of  wood. 

The  Aftoman  Deposits 

25  ft.  Beginning  with  87  feet  a  part  of  the  clay  does  not  effervesce.  In 
the  next  foot  the  effervescence  is  still  less,  and  in  the  third  foot 
(the  8gth)  the  last  lime  concretion,  one  inch  in  diameter,  appears. 
The  clay  is  on  the  whole  a  dark  grayish  blue,  but  grades  back 
and  forth  from  black  to  light  blue.  Minute  rootlike  fragments 
of  vegetation  are  scattered  through  it  but  no  fragment  of  wood 
was  found.  At  95  feet  is  a  layer  of  moss  and  black  dirt  about  an 
inch  thick;  a  foot  deeper  is  a  similar  layer.  In  these  old  soils 
were  a  few  small  pebbles  of  greenstone,  black  chert,  quartz,  and 
limestone,  to  the  last  of  which  the  slight  effervescence  seemed 
to  be  due.  The  largest  greenstone  pebble  was  JXjXi  inch; 
the  fragments  of  limestone  were  IXyVX-ft-  inch  and  \  X fXi  inch. 
In  the  next  foot  (the  97th)  there  was  another  layer  ij  inches 
thick  of  this  old  black  soil  and  moss,  and  in  the  next  foot  two 
inches  more  like  an  impure  peat.  Between  these  two  layers 
was  an  angular  fragment  of  limestone  iXfXf  inch.  In  the 
next  nine  feet  (to  106  feet)  there  were  no  pebbles  and  the  grit 
was  very  fine,  the  largest  particle  being  a  particle  of  greenstone 
rV  of  &n  inch  in  diameter  at  106  feet. 

At  107  feet  from  the  surface  the  grayish-blue  clay  contained 
traces  of  a  brownish  sand,  the  largest  grain  of  which  was  a  green- 
.  stone  JXlXyV  mcn-  A  foot  deeper  (at  108  ft.)  several  sub- 
angular  pebbles  of  greenstone  were  encountered,  one,  the  largest, 
JXiXf  inch;  another,  iXfX|  inch;  another,  fX|Xf  inch 
and  subangular  in  shape.  For  the  next  two  feet  (108  and  109) 
the  dark-grayish  clay  was  streaked  with  brown  sand  and  con- 
tained minute  pebbles,  the  largest  of  which  was  a  chert  f 


IO 


PLEISTOCENE   DEPOSITS   IN   WARREN   COUNTY,    IOWA 


inch.  The  next  half-foot  was  a  grayish  clay  with  streaks  of 
brown  sand,  and  with  gravel  at  its  base.  Within  the  next  few 
inches  came  a  bed  of  gravel,  described  as  follows : 

The  gravel  was  nearly  a  foot  in  thickness,  coarse  above, 
fine  below,  with  a  half-inch  streak  of  red  clay  in  the  midst  of  it. 

The  greenstones  of  the  gravel  were  rounded  and  subangular, 
all  smooth  and  un  weathered,  four  striated;  one  especially,  flat 
and  striated  on  one  side,  rounded  on  the  other,  and  pitted  in 
three  places,  the  edges  and  solid  angles  rounded  and  polished — 
a  typical  glacial  pebble.  One  limestone  fragment  contained 
part  of  a  shell — like  a  fragment  of  Productus  muricatus,  the  index 
fossil  of  the  Des  Moines  formation. 


The  complete  analysis  of  this  gravel  is  as  follows,  all  excepting  the 
very  finest  material  being  used  in  making  the  analysis : 

ANALYSIS  OF  GRAVEL  FOUND  IN  THE  BASE  OF  THE  AFTONIAN  DEPOSIT 
(DERIVED  FROM  SUB-AFTONIAN  DRIFT) 


U«a 

Number  Found 

Percentages 
All  Material 

Percentages 
Foreign  Material 
Only 

Limestone,  gray,  many  angular,  one  with  a 
fragment  like  Productus  muricatus,  the 
index  fossil  of  the  Des  Moines  forma- 
tion.    This  is  all  to  be  classed  as  local 
material,  and  is  possibly  derived  from 
the  very  stratum  on  which  the  gravel 
rests 

63 

18.4 

o.o 

Greenstone,  four  striated,  many  rounded 
and  sub-angular                             

148 

44.  1 

57-4 

Sandstone,  gray  (local)  
Sandstone  (not  local)  
Granite,  all  but  four  light  colored  
Quartz  

15 
6 
29 
33 

4-4 
1.8 
8.6 
9.8 

o.o 
2-3 
n-3 

12.8 

Chert,  brown  

15 

4-4 

5-9 

Chert  dark 

c 

I  .  C 

i  .9 

Chert  light 

4 

I  .  2 

i  .5 

Quartzite  pink                                   

2 

0.6 

0.8 

Quartzite,  dark  
Quartzite,  light  
Schistose  rocks  

3 
6 

0.9 

2.  I 

1.8 

i  .  i 

2.7 
2.3 

336 

99.6 

IOO.O 

In  the  above  table  the  first  column  of  figures  expresses  the  exact 
number  of  pebbles  found;  the  second,  the  percentages  of  all  the  pebbles; 
and  the  third,  the  percentages  of  the  foreign  material  only. 


RECORD  OF  SIMPSON  COLLEGE  WELL 


II 


If  in  the  above  that  which  is  local  in  character  be  excluded,  all  the 
remainder  are  of  a  very  resistant  character,  not  a  single  specimen  being 
found  of  the  decomposed  granite  so  common  at  the  surface  of  the  Kansan 
drift.  The  largest  of  the  granites  has  a  rough  surface  such  as  may  be 
found  in  a  granite  of  similar  texture  scaling  under  the  action  of  frost. 
The  almost  complete  absence  of  pink  quartzites  is  also  a  notable  fact 
when  comparing  the  analysis  with  analyses  of  pebbles  from  the  Kansan. 

The  sizes  of  the  largest  pebbles  are  as  follows : 


Limestone 

4  Xif  Xif  inches 
3fX3   X2 
3^X2  Xi 

3 


Greenstone 

4-2X3  X2    inches 
3  X3  X  f 
3  X2lXif 


2^X2  Xi 
2fXifXi 


Quartz 

4  X2^Xif  inches 
3  X 


iixi  x  f 

i   X  fX  f 
fX  1 


Granite 

3^X3  X  if  inches 

3^X31X2 

3  X2^X2 

2fXlfX2 

2^X2  Xi| 


Pink  Quartzite 

f  inches 

Carboniferous 

The  bottom  of  the  well  is  on  a  hard,  flat  rock,  which  is  undoubtedly 
a  Carboniferous  stratum  in  place,  and  presumably  the  source  of  many 
of  the  limestone  pebbles  found  in  the  gravel. 

THE   WATER 

The  character  of  the  water  obtained  through  the  gravel  bears  evi- 
dence of  the  presence  of  partially  decomposed  vegetation  (Aftonian). 
The  water  is  so  charged  with  free  ammonia  that  the  quantity  of  this 
ammonia  was  not  determined.  The  albumenoid  ammonia  present  was 
found  to  be  thirty-two  one-hundredths  of  a  part  per  million.1 

DISCUSSION 

In  the  above  description  the  material  down  to  the  weathered  surface 
of  the  Kansan  is  what  is  commonly  found  throughout  the  upland  in  the 
central  part  of  the  county.  Parts  of  it  correspond  to  what  has  been 
described  in  other  places  where  the  Kansan  is  the  surface  drift. 

1  The  analysis  was  made  by  Professor  C.  J.  Holmes. 


12  PLEISTOCENE   DEPOSITS   IN   WARREN   COUNTY,    IOWA 

From  the  top  of  this  drift,  at  thirty-two  feet,  down  to  the  bottom  of 
the  drift,  at  eighty-six  feet,  the  characteristics  of  the  deposit  are  so 
like  those  of  the  Kansan  drift,  and  the  gradations  so  perfect  from  a 
weathered  portion  to  an  unweathered  portion  below,  that  there  seems 
no  possibility  whatever  that  it  includes  more  than  one  drift  sheet.  It 
is  therefore  all  classed  as  Kansan. 

The  deposit  that  underlies  the  Kansan  is  peculiar.  The  color  of 
the  deposit  and  the  presence  of  a  few  pebbles  within  the  twenty-five 
feet,  though  the  pebbles  are  only  about  half  an  inch  in  diameter,  suggest 
sub-Aftonian  drift;  but  the  appearance  of  stratification,  marked  espe- 
cially by  the  distinct  layers  of  moss  with  accompanying  black  dirt,  at 
least  four  of  which  were  conspicuous,  are  not  characteristics  of  drift 
at  all  but  of  a  non-glacial  deposit  into  which  it  seems  possible  such 
small  pebbles  may  have  been  washed,  though  no  stratum  of  gravel 
associated  with  them  within  the  deposit  was  noted.  Such  a  deposit, 
between  a  Kansan  above  and  a  sheet  of  gravel  below  that  contains 
glaciated  pebbles,  is  classed  as  a  part  of  the  Aftonian  interglacial  deposit. 
The  deposit  appears  to  be  a  unit,  though  varying  slightly  close  to  the 
gravel  at  its  base. 

The  stratum  of  gravel  with  glaciated  pebbles  at  the  bottom  of  the 
well  must  have  come  from  a  glacial  deposit  antedating  the  Aftonian. 
It  was  therefore  derived -from  the  sub-Aftonian  drift,  for  no  other  drift 
sheet  is  known  from  which  it  may  have  come.  The  conditions  suggest 
that  the  well  reaches  the  bottom  of  a  ravine  into  which  gravel  from 
sub-Aftonian  drift  was  washed. 

The  sub-Aftonian  drift  is  wanting  at  this  particular  place,  but  it 
is  not  wanting  in  various  parts  of  the  county.  The  Kansan  may  be  seen 
in  its  usual  aspects  in  the  higher  ground,  while  along  the  deeply  cut 
trenches  in  ravines  may  be  seen  the  dense,  bluish-black  sub-Aftonian, 
largely  free  from  bowlders  and  pebbles.  The  soil  washed  from  the 
hillsides  generally  covers  the  dividing  surface  between  the  two  drifts  and 
whatever  of  Aftonian  may  remain. 


THE  SUB-AFTONIAN  DRIFT 

THE  NAME 

For  sub-Aftonian,  or  pre-Kansan,  drift  several  names  have  been  pro- 
posed. Albertan  seems  inapplicable  since  the  deposit  that  first  received 
that  name  is  found  to  be  non-glacial  in  origin.1  The  Jersey  an  of  New 
Jersey2  has  been  so  traced  in  its  relations  to  deposits  in  the  Mississippi 
Valley3  that  that  name  may  prove  an  acceptable  term,  but,  though 
already  used  in  Iowa,4  the  exact  relation  of  the  deposit  as  an  equivalent  of 
the  sub-Aftonian  drift  of  Iowa  does  not  yet  seem  to  be  thoroughly  estab- 
lished. Recently  Shimek,5  at  the  suggestion  of  Calvin,  has  proposed  the 
name  Nebraskan.  This  term  has  been  applied  to  a  "tough,  impervious 
bluish-black  till"  containing  pebbles  of  greenstone,  white  quartzite,  and 
light-colored  granite,  and  lying  beneath  the  Aftonian  interglacial 
deposits. 

THE   SUB-AFTONIAN  DRIFT  IN   GENERAL 

Till  of  such  a  character  still  visible  in  small  exposures  has  been 
described  as  lying  beneath  the  Aftonian  near  Thayer  and  Afton  Junc- 
tion, Iowa.6  It  is  found  near  Council  Bluffs,  Iowa,7  and  across  the 
Missouri  River  in  Nebraska.  It  appeared  in  the  railroad  cut  at  Oelwein8 

1  Fred  H.  H.  Calhoun,  "The  Montana  Lobe  of  the  Keewatin  Ice  Sheet,"  Pro- 
fessional Paper,  U.S.  Geological  Survey,  No.  50,  pp.  50-51  and  57. 

2  Rollin  D.  Salisbury,  "The  Glacial  Geology  of  New  Jersey,"  Geological  Survey  of 
New  Jersey,  Vol.  V,  1902,  p.  189. 

3  Chamberlin  and  Salisbury,  Geology,  Vol.  Ill,  pp.  384-88. 

4  W.  H.  Norton,  "Geology  of  Bremer  County,"  Iowa  Geological  Survey,  Vol. 
XVI,  p.  362. 

5  B.  Shimek,  Addendum  to  paper  on  "Aftonian  Sands  and  Gravels  in  Western 
Iowa,"  Bulletin  of  the  Geological  Society  of  America,  Vol.  XX,  p.  408. 

6H.  F.  Bain,  "The  Aftonian  and  Pre-Kansan  Deposits  of  Southwestern  Iowa," 
Proceedings  of  the  Iowa  Academy  of  Sciences,  Vol.  V  (189 7),  p.  96;  S.  Calvin,  "The 
Aftonian  Gravels  and  Their  Relation  to  the  Drift  Sheets  of  the  Region  about  Afton 
Junction  and  Thayer,"  Davenport  Academy  of  Natural  Sciences,  Vol.  X  (1907),  pp. 
22  and  29. 

7  B.  Shimek,  Addendum  cited. 

8  Grant  E.  Finch,  "Drift  Section  at  Oelwein,  Iowa,"   Proceedings  of  the  Iowa 
Academy  of  Sciences,  Vol.  IV  (1896),  pp.  54-58;   S.  W.  Beyer,  "Evidence  of  a  Sub- 
Aftonian  Till  Sheet  in  Northeastern  Iowa,"  ibid.,  Vol.  IV  (1896),   pp.    59-62;    S. 
Calvin,  "Summary  of  Discussion,"  ibid.,  Vol.  IV  (1896),  pp.  66-68. 


14  PLEISTOCENE   DEPOSITS   IN   WARREN   COUNTY,    IOWA 

and  in  an  excavation  at  Muscatine.1  Evidences  of  the  presence  of  a 
pre-Kansan  drift  have  been  found  in  other  places.2 

Such  a  bowlder  clay  differs  from  the  tough  bluish-black  Carbon- 
iferous shale  in  the  total  absence  of  such  stratification  as  is  found  in  the 
shale,  and  in  the  presence  of  pebbles  (though  generally  rare)  found  in 
the  drift  but  not  in  the  shale.  It  differs  from  the  Kansan  bowlder  clay 
in  the  presence  of  a  much  lower  proportion  of  fine  sand  and  coarse  grit 
than  is  found  in  the  Kansan,  rendering  the  Kansan  much  less  imper- 
vious to  water  than  the  sub-Aftonian  and  much  more  easily  eroded. 
Marks  of  a  steam  shovel,  presumably  made  in  the  spring  of  1903  when 
extensive  work  was  done  along  the  line  of  the  Chicago,  Burlington  and 
Quincy  Railroad,  may  still  be  seen  (1910)  on  the  sub-Aftonian  drift 
exposed  in  tjie  second  railroad  cut  west  of  Thayer.  No  such  evidence 
is  now  visible  on  the  Kansan.  The  character  of  the  pebbles  seen  in  the 
gravel  at  Af  ton  Junction  appears  to  the  eye  to  accord  with  the  statement 
that  they  have  a  high  percentage  of  white  quartz  and  light-colored 
granite.  In  the  pebbles  found  at  the  bottom  of  the  Simpson  College 
well,  and  carefully  tabulated,  the  scarcity  of  pink  quartzites  was  noted 
and  the  relative  abundance  of  quartz  and  light-colored  granites.  The 
at  least  general  absence  of  bowlders  more  than  six  or  eight  inches  in 
diameter  also  seems  to  contrast  the  sub-Aftonian  with  the  Kansan  in 
which  bowlders  up  to  a  foot  or  more  in  diameter  are  common. 

The  impervious  and  tough  character  of  the  clay  that  has  enabled  it 
to  resist  weathering  so  as  still  to  bear  the  marks  made  by  a  steam  shovel, 
enables  steep  sides  of  trenches  cut  in  clay  of  this  character  in  the  valley 
bottoms  to  stand  vertically  for  a  long  time.  Along  such  trenches  where 
the  clay  has  been  found  weathered,  the  color  of  the  sub-Aftonian  changes 
to  a  seal  brown,  the  toughness  of  the  clay  persisting,  thus  contrasting 
in  color  and  tenaciousness  with  the  light-yellow  clay  into  which  the 
Kansan  clay  weathers.  The  hills  of  sub-Aftonian  still  left  standing, 
though  mantled  with  Kansan  and  later  deposits,  are  steeper  than  the 
hills  of  Kansan  drift  where  the  Kansan  is  thick.  This  relative  steepness 
is  noteworthy  near  Thayer  and  Afton  Junction,  and  across  the  country 
northeastward  into  Warren  County,  throughout  which  distance  the 
same  type  of  topography  and  the  same  character  of  deep-lying  clay 
(sub-Aftonian)  are  found. 

1  J.  A.  Udden,  "Geology  of  Muscatine  County,"  Iowa  Geological  Survey,  Vol.  IX, 
P-  338. 

2  See  the  following  county  reports  in  the  Iowa  Geological  Survey:   T.  E.  Savage, 
"Geology  of  Benton  County,"  Vol.  XV,  p.  201;  and  "Geology  of  Fayette  County," 
Vol.  XV,  p.  522;  W.  H.  Norton,  "Geology  of  Bremer  County,"  Vol.  XVI,  p.  362. 


THE    SUB-AFTONIAN   DRIFT  15 

THE  DISTRIBUTION  AND  RELATION  OF   THE   SUB-AFTONIAN  DRIFT  IN 
WARREN   COUNTY 

In  all  parts  of  Warren  County  a  deep-lying  bowlder  clay  of  the  char- 
acter already  described  may  be  seen,  especially  in  the  southern  and 
western  portions.  That  a  clay  of  this  character  should  be  classed  as 
separate  from  the  Kansan  and  entirely  distinct  from  it,  is  a  proposi- 
tion difficult  to  prove  in  many  parts  of  the  county,  but  fortunately  there 
are  places  where  the  relation  is  perfectly  evident,  as  half  a  mile  east  of 
New  Virginia,  and  four  miles  to  the  northeast  (Sections  7  and  18  of 
Squaw  Township),  and  a  mile  south  of  St.  Marys. 

Half  a  mile  east  of  New  Virginia  (the  N.W.  i  of  the  S.E.  \  of  Sec.  27) 
the  bed  of  the  ravine  is  on  the  tough  and  impervious  bluish-black  sub- 
Aftonian  clay  containing  small  pebbles  of  greenstone,  white  quartz, 
chert,  and  granite.  The  section  as  a  whole  is  as  follows: 

i  ft.     Soil;  pebbles  to  within  two  inches  of  the  surface. 

i  ft.    Gravel,  a  recent  surface  wash. 

5  ft.    Clay,  yellowish,  very  few  pebbles;   bluish  in  trench  near  by. 

Kansan  drift 

7  in.    Sand,  fine,  mostly  white  but  somewhat  stained  by  iron.    Top  of  Aftonian 
\  in.    Sand,  deeply  stained  to  reddish  brown. 
3  in.    Sand,  fine,  black. 

7  ft.    Sand,  fine,  no  stratification  evident,  reddish  brown  where  damp,  light 
yellowish  brown  where  dry. 

5  in.    Sand,  stratified,  cemented  by  iron  and  calcium  carbonate. 

Bottom  of  Aftonian 

6  in.    (Exposed.)     Clay,  bluish  black,  with  small  pebbles  of  greenstone,  white 

quartz,  chert,  and  granite.  Sub- Aftonian 

Erosion  later  (1910)  than  the  above  section  was  measured  has  brought 
to  light  two  bowlders  each  a  foot  in  diameter  in  the  Kansan  drift  over- 
lying the  sand. 

In  the  railroad  cut  at  the  New  Virginia  station  the  Kansan  drift  is 
only  ten  feet  thick,  the  Aftonian  sand  appears  about  the  middle  of  the 
cut,  and  the  sub-Aftonian  clay  is  imperfectly  exposed  for  about  ten 
feet  down  to  the  level  of  the  track. 

A  further  relation  of  the  sub-Aftonian  is  evident  at  and  near  Igo's 
stock  farm  in  Squaw  Township  (the  southwestern  part  of  Section  18). 
Here  the  Aftonian  sand  extends  over  the  brow  of  the  hill  down  into  the 
ravine  to  the  west,  thus  mantling  a  hill  of  sub-Aftonian  drift  which 
rises  about  a  hundred  feet  above  adjacent  valleys,  where  the  sub-Aftonian 
drift  is  still  so  thick  that  it  is  not  cut  through  in  the  bottom  of  the  ravine. 


1 6  PLEISTOCENE    DEPOSITS   IN   WARREN   COUNTY,    IOWA 

The  hill  itself  is  covered  by  a  thin  deposit  of  Kansan  drift,  the  latter 
where  exposed  completely  weathered  into  a  light-yellowish  bowlder 
clay.  Near  the  northeast  corner  of  this  section  (but  in  the  S.E.  J  of  the 
S.E.  J  of  Sec.  7)  is  a  good  exposure  by  the  roadside.  Here  about  six 
inches  of  sand  deeply  stained  by  oxidized  iron  lies  immediately  beneath 
a  black  layer-like  old  soil  and  rests  on  a  clay  that  is  undoubtedly  sub- 
Aftonian. 

A  mile  south  of  St.  Marys  the  brown  Aftonian  sand  lies  by  the  road- 
side beneath  yellowish  and  bluish  Kansan  drift  filled  with  pebbles  and 
cobbles,  with  a  large  Kansan  bowlder  perhaps  four  feet  long  near  at  hand. 
In  a  ravine  to  the  east  the  sub-Aftonian  has  been  trenched  to  a  depth 
of  perhaps  twenty-five  feet  below- the  Aftonian  without  exposing  the 
Carboniferous. 

Along  the  deeply  cut  trenches  of  the  southern  and  western  townships 
of  the  county  may  be  seen  the  tough  bluish-black  clay  of  the  same  general 
character  as  that  above  described,  while  the  more  sandy  and  more  com- 
pletely oxidized  Kansan  appears  on  the  hillsides.  The  relation  is  well 
illustrated  also  near  Churchville  in  the  northwestern  part  of  the  county. 
The  large  granite  bowlders  to  be  seen  by  the  track  just  north  of  the 
railroad  station  at  Churchville  are  in  the  Kansan  drift.  Following 
down  the  ravine  to  the  northeast  other  large  bowlders  appear  on  the 
side  and  even  near  the  level  of  the  valley  bottom,  but  the  trench  itself 
is  cut  into  a  tenacious  partly  weathered  clay.  Here  whatever  Kansan 
may  have  previously  mantled  the  sub-Aftonian  drift  is  now  largely 
removed  and  whatever  may  be  left  is  now  concealed  beneath  soil  washed 
down  the  valley  sides,  with  no  Aftonian  in  sight.  In  one  of  the  trenches 
south  of  Churchville  no  Kansan  is  in  sight  throughout  the'  entire  length 
of  the  ravine,  though  it  may  be  found  in  a  ravine  to  the  west. 

In  the  northeast  half  of  the  county  exposures  of  Carboniferous  are 
of  frequent  occurrence,  but  even  here  along  the  deeper  portions  of  the 
valleys  the  Carboniferous  is  concealed  by  clay  of  the  sub-Aftonian  type. 
East  of  Milo  and  west  of  Lacona  it  lies  along  and  beneath  the  ravines. 
On  the  county  line  southeast  of  Lacona  it  outcrops  half-way  up  the  hill- 
side, just  below  Aftonian  sand  which  lies  below  a  thin  Kansan. 

While  data  of  what  lies  beneath  the  Aftonian  of  the  river  valleys 
are  scarce,  it  is  apparently  this  same  phase  of  clay  that  is  found  in  the 
forty-five  feet  beneath  the  level  of  the  river  bed  in  the  northeastern 
portion  of  Virginia  Township,  that  fills  at  least  a  portion  of  the  sixty- 
five  feet  down  to  the  Carboniferous  beneath  the  bed  of  North  River  in 
Greenfield  Township,  and  that  occupies  the  concealed  valleys  of  Jackson, 


THE   SUB-AFTONIAN  DRIFT  17 

Jefferson,  Linn,  Lincoln,  and  Greenfield  townships,  mentioned  when 
describing  the  drift  as  a  whole. 

Such  well  records  as  are  obtainable  are  not  sufficiently  detailed  to 
be  of  service  in  determining  what  is  sub-Aftonian  as  contrasted  with 
Kansan,  except  where  a  definite  Aftonian  is  so  evident  as  to  attract 
the  attention  of  the  one  digging  the  well. 

GRAVEL  FROM   THE   SUB-AFTONIAN  DRIFT,   IN  WELLS 

Further  evidence  concerning  the  sub-Aftonian  drift  is  recognized 
in  the  Aftonian  gravel  found  in  wells.  In  two  of  the  forty-two  wells 
in  which  Aftonian  gravel  was  found  the  gravel  is  distinctly  described 
as  a  coarse  gravel,  the  stones  of  which  are  three  or  four  inches  in  diameter. 
These  are  in  Section  30  of  Squaw  Township  and  at  the  college  well,  the 
record  of  which  has  been  given  in  detail.  In  the  college  well  the  sub- 
angular,  polished,  and  striated  condition  of  some  of  the  pebbles  gives 
conclusive  evidence  of  glacial  action,  and  the  position  at  the  bottom  of 
an  Aftonian  deposit  twenty-five  feet  thick  indicates  that  these  pebbles 
must  have  come  from  a  sub-Aftonian  drift. 

A  statement  of  the  percentages  of  the  different  kinds  of  rocks  among 
the  pebbles  of  the  gravel,  at  the  base  of  the  Aftonian  deposits  at  the 
Simpson  College  well,  may  be  found  in  the  record  already  given.  If 
this  description  be  compared  with  that  of  the  sub-Aftonian  (pre-Kansan) 
pgbbles  of  Muscatine  County1  in  the  eastern  part  of  the  state,  one  point 
of  similarity  and  several  points  of  difference  are  noted.  In  both  places 
the  limestone  pebbles  are  the  most  numerous.  In  Warren  County 
they  are  unquestionably  local  and  probably  not  derived  from  a  sub- 
Aftonian  drift;  in  Muscatine  County,  at  least  a  part  of  the  limestone 
pebbles  are  local.  The  greenstones  are  the  next  most  abundant,  but 
they  are  more  abundant  in  Warren  County  than  in  Muscatine  County. 
The  chert  comes  next  in  abundance  at  each  place,  and  of  material  which 
is  distinctly  not  local,  it  is  present  in  about  equal  quantities  in  the  two 
places.  The  quartz,  the  quartzite,  and  both  dark  and  light  granites 
are  all  relatively  more  abundant  in.  Warren  County  than  in  Muscatine 
County.  The  schistose  rocks,  though  few,  are  more  abundant  in  Mus- 
catine than  in  Warren  County.  Jasper  is  not  found  at  either  place. 

If  the  statement  concerning  the  Aftonian  gravels  gives  the  names 
of  the  rocks  in  the  order  of  their  relative  abundance,  the  statement 

1  J.  A.  Udden,  "Geology  of  Muscatine  County,"  Iowa  Geological  Survey,  Vol.  IX, 
P-  336. 


1 8  PLEISTOCENE   DEPOSITS   IN   WARREN   COUNTY,    IOWA 

for  Muscatine  County,1  "yellow  chert,  greenstone,  white  quartz,  and 
red  granite  were  the  prevailing  rocks,"  becomes  the  following  for  Warren 
County:  greenstone,  quartz,  light-colored  granite,  and  brown  chert 
were  the  prevailing  rocks. 

GRAVEL  FROM  THE   SUB-AFTONIAN  DRIFT,   IN  OUTCROPS 

In  Section  16  of  Jefferson  Township  (S.W.  £  of  the  S.W.  i)  a  bed  of 
small  Aftonian  pebbles  of  dark  chert  and  greenstone  lies  close  to  the 
Carboniferous  and  beneath  Aftonian  sand  overlain  by  Kansan  drift. 
The  gravel  was  undoubtedly  left  from  the  erosion  of  the  sub-Aftonian 
drift,  but  the  drift  itself  is  not  visible  at  that  point.  Across  the  road, 
west  of  Section  30  of  Virginia  Township  (but  in  Madison  County),  is 
a  small  deposit  of  gravel  that  is  judged  to  be  Aftonian  because  of  the 
presence  of  a  distinct  Aftonian  near  by  between  Kansan  and  sub-Aftonian 
drifts.  At  numerous  places  along  the  roads  in  the  northeastern  half 
of  the  county  and  at  some  places  in  ravines,  the  Kansan  drift  thins  out 
close  to  the  Carboniferous.  The  pebbles  and  bowlders  there  found 
seem  derived  from  the  Kansan,  but  some  of  them  may  have  come  from 
the  sub-Aftonian  drift. 

ON   THE   THICKNESS   OF   THE   SUB-AFTONIAN   NOW   REMAINING 

In  the  southern  half  of  the  county  the  sub-Aftonian  drift  frequently 
lies  perhaps  forty  feet  below  the  surface  of  the  upland.  In  the  north- 
eastern half  of  the  county  the  surface  of  the  sub-Aftonian  appears  to 
lie  much  farther  below  the  level  of  the  upland,  perhaps  eighty  feet. 
Assuming  these  estimates  to  be  correct,  substracting  them  from  the  pres- 
ent relief,  and  adding  the  approximate  depth  of  the  drift  below  the 
present  river  beds,  and  assuming  that  at  some  points  the  drift  extends 
from  the  highest  level  at  which  it  is  found  to  the  lowest  level,  we  have 
an  estimate  of  the  present  maximum  thickness  of  the  sub-Aftonian 
drift  as  follows: 

Feet  Feet 

Linn 135  Jackson 175 

Greenfield 145  White  Oak 175 

Allen 135  Otter 174 

Richland 156  Belmont 175 

Jefferson 140  Virginia a.  209 

Lincoln  and  Greenfield  .  153  Squaw *.  142 

Lincoln  and  Palmyra.  . .  153  Liberty 122 

Union 130  White  Breast 175 

1  J.  A.  Udden,  "  Geology  of  Muscatine  County,"  Iowa  Geological  Survey,  Vol.  IX, 
P-  339- 


THE    SJJB-AFTONIAN  DRIFT  19 

On  such  an  estimate  the  thickness  of  the  sub-Aftonian  (including 
possibly  subglacial  surface  deposits)  would  now  vary  from  o  to  209  feet 
with  an  average  maximum  of  156  feet.  This  approximately  coincides 
with  the  estimated  present  relief  in  each  township;  the  average  maximum 
thickness  in  the  county  as  a  whole  is  but  -six  feet  less  than  the  average 
estimated  relief  (which  is  162  feet).  There  is  no  evidence  as  to  the 
amount  eroded  from  the  former  surface  of  the  sub-Aftonian  drift,  nor 
any  evidence  as  to  the  character  of  that  former  surface,  except  as  pre- 
served in  the  present  general  plan  of  the  drainage.  No  evidence  what- 
ever has  been  found  of  former  kames  or  drumlins,  the  drift  presenting 
the  general  appearance  of  a  ground  moraine  from  which  all  evidence  as 
to  former  surface  has  been  eroded. 

This  sub-Aftonian  drift  does  not  simply  mantle  the  Carboniferous 
surface.  In  places  it  lies  in  Carboniferous  valleys  and  in  other  places 
still  exists  as  hills  of  sub-Aftonian  drift,  with  no  Carboniferous  evident 
near  at  hand.  In  valleys  cut  in  this  deposit  lies  the  present  drainage 
plan,  in  almost  complete  disagreement  with  the  preglacial  drainage 
lines,  with  the  sub-Aftonian  thickest  beneath  the  present  upland  above 
the  preglacial  valleys.  With  such  a  relation  of  the  sub-Aftonain  in 
position  and  in  thickness,  and  with  the  Kansan  drift  in  some  places 
simply  mantling  the  sub-Aftonian  drift  with  little  or  no  Aftonian  inter- 
glacial  deposits  between,  it  is  evident  that  the  sub-Aftonian  drift  was 
thick  enough  to  obscure  the  preglacial  topography  and  to  necessitate 
the  development  of  a  new  drainage  plan  in  Aftonian  times. 


THE  AFTONIAN  INTERGLACIAL  DEPOSITS 

THE   NAME 

The  term  Aftonian  was  first  applied  by  Chamberlin1  to  the  inter- 
glacial  gravel  lying  beneath  what  is  now  called  Kansan  drift  and  over 
the  sub-Aftonian  near  Afton  Junction,  Iowa. 

THE   GENERAL   CHARACTER   OF   THE  AFTONIAN   DEPOSITS 

Gravels  of  Aftonian  age  and  peat  bogs  have  since  been  found  in 
other  parts  of  Iowa  and  the  deposits  described,  notably  near  Oelwein, 
Tama,  and  Council  Bluffs.  From  the  amount  and  state  of  preservation 
of  the  fossil  contents  of  the  gravels  Calvin  now  thinks  that  both  fossils 
and  gravels  were  not  laid  down  by  floods  at  the  beginning  nor  at  the 
close  of  the  interglacial  interval,  but  "record  conditions  which  existed  at 
some  time  during  the  progress  of  the  interval,"2  a  conclusion  with  which 
data  with  reference  to  the  deposit  in  Warren  County  are  in  full  accord. 

In  Warren  County  the  Aftonian  deposit  may  be  divided  into  two 
portions,  a  lower  portion  consisting  of  gravel  and  stratified  sand,  and  an 
upper  portion  which  in  the  college  well  appears  to  be  a  low-ground  deposit 
like  old  soil,  but  in  other  places  on  higher  ground  there  is  a  fine  sand;  so 
that  the  deposits  either  change  from  a  gravel  into  an  old-soil-like  deposit 
above,  or  grade  from  a  gravel  or  coarse  sand  below  into  a  finer  sand 
above.  The  lower  portions  of  the  stratified  sand  contain  layers  of  old 
soil  and  bands  of  oxide  of  iron,  marking  former  surfaces,  the  whole  resting 
unconformably  upon  the  sub-Aftonian,  or  upon  the  Carboniferous  where 
preglacial  deposits  and  the  sub-Aftonian  have  been  eroded. 

An  old-soil-like  deposit  grading  back  and  forth  from  black  to  light 
blue,  with  its  bands  of  moss  and  black  dirt,  is  minutely  described  in 
the  record  of  the  Simpson  College  well  already  given. 

Thick  beds  of  coarse  gravel  like  those  to  be  found  at  Afton  Junction 
are  not  found  in  the  county,  though  a  small  outcrop  may  be  found  a 
few  feet  west  of  the  county  line  at  Section  30  of  Virginia  Township. 
Deposits  with  fragments  of  trees  have  been  found  in  places  that  are 
probably  Aftonian,  but  in  general  the  Aftonian  in  the  upland  of  the 
county  does  not  contain  evidence  of  an  extensive  forest.  Such  evidence 

1  T.  C.  Chamberlin,  Editorial,  Journal  of  Geology,  Vol.  Ill  (1895),  p.  272. 

2  S.  Calvin,  "Present  Phase  of  the  Pleistocene  Problem  in  Iowa,"  Bulletin  of  the 
Geological  Society  of  America,  Vol.  XX  (1909),  p.  138. 

20 


THE   AFTONIAN   INTERGLACIAL  DEPOSITS  21 

seems  confined  to  parts  of  the  lower  Aftonian  water  courses.  The  total 
absence  of  wood  in  the  twenty-five  feet  of  Aftonian  in  the  college  well  is 
noteworthy. 

VARIOUS   EXPOSURES   OF   THE  AFTONIAN 

The  exposure  of  the  Aftonian  half  a  mile  east  of  New  Virginia  will 
be  mentioned  first  because  of  the  relation  there  evident.  The  section 
is  here  repeated  in  full: 

i  ft.     Soil,  containing  pebbles  to  within  two  inches  of  the  surface. 

i  ft.     Gravel,  a  surface  wash. 

5  ft.  Clay,  yellowish,  very  few  pebbles,  bluish  in  a  trench  near  by.  Later 
erosion  revealed  two  bowlders  each  a  foot  in  diameter,  within  the  body 
of  the  drift.  Kansan  drift 

7  in.    Sand,  fine,  mostly  white  but  somewhat  stained  by  iron  oxide. 

Top  of  Aftonian 

\  in.    Sand,  deeply  stained  to  reddish  brown. 

3  in.    Sand,  fine,  black. 

7  ft.  Sand,  fine,  no  stratification  evident,  reddish  brown  where  damp,  light 
yellowish  where  dry. 

5  in.    Sand,  stratified,  cemented  by  iron  and  calcium  carbonate. 

Bottom  of  Aftonian 

6  in.    (Exposed.)     Clay,  bluish  black,  with  small  pebbles  of  greenstone,  white 

quartz,  chert,  and  granite.  Sub-Aftonian 

(In  tests  with  acid  at  perhaps  a  dozen  different  places  this  is  the  only 
locality  where  the  sub-Aftonian  effervesced  at  its  surface.) 

In  the  railroad  cut  at  New  Virginia  station  the  fine  sand  appears 
within  ten  feet  of  the  top  of  the  cut.  In  Section  7  of  Squaw  Township 
(S.E.  |  of  the  S.E.  J)  six  inches  of  sand  stained  deeply  by  oxide  of  iron 
lies  immediately  beneath  a  black  layer-like  old  soil  and  rests  on  a  clay 
that  is  undoubtedly  sub-Aftonian.  At  Igo's  farm  previously  mentioned 
(Section  18)  a  deeply  stained  brown  sand  lies  beneath  the  general  body 
of  the  sand.  In  the  valley  southwest  the  same  relation  is  also  evident, 
the  entire  relation  emphasizing  the  fact  that  here  the  sand  mantles  a 
hill  of  sub-Aftonian  drift.  By  the  roadside  a  mile  southeast  of  St. 
Marys  and  at  the  south  end  of  the  railroad  cut  at  Churchville  are  deposits 
of  this  fine  sand,  though  at  present  both  deposits  are  concealed.  In  a 
ravine  near  the  latter  place  (the  S.W.  J  of  the  S.W.  J  of  Section  16,  Jeffer- 
son Township)  and  resting  on  three  feet  of  Carboniferous  shale,  decom- 
posed coal,  and  weathered  sandstone,  lies  a  deposit  of  stratified  sand  and 
gravel  stained  with  oxide  of  iron,  varying  from  two  to  ten  feet  in  thick- 


22  PLEISTOCENE   DEPOSITS   IN   WARREN   COUNTY,    IOWA 

ness,  above  the  highest  level  of  which  lies  a  bowlder  about  two  and  a 
half  feet  in  diameter — a  Kansan  bowlder.  The  numerous  small  rounded 
pebbles  near  the  base  are,  of  course,  from  the  sub-Aftonian  drift,  but  that 
drift  itself  is  not  visible  at  this  point. 


AFTONIAN  SAND  AND  GRAVEL 

An  exposure  of  Aftonian  sand  and  gravel  may  be  found  in  Section  16  of  Jefferson 
Township  (S.W.  \  of  the  S.W.  |).  Here,  resting  on  three  feet  of  Carboniferous  shale, 
decomposed  coal,  and  weathered  sandstone,  lies  a  deposit  of  sand,  thickness  not  known 
because  of  slumping,  above  the  highest  level  of  which  lies  Kansan  drift  partially 
imbedded  in  which  is  a  bowlder  about  two  and  a  half  feet  in  diameter.  At  the  base  of 
the  sand  (back  of  the  hammer)  is  a  thin  deposit  of  small  pebbles  (dark  chert  and 
greenstone).  There  is  nothing  left  in  sight  of  the  sub-Aftonian  drift  from  which  the 
pebbles  were  derived. 

At  the  Avon  gravel  pit  in  Polk  County  just  north  of  Allen  Township, 
a  broad  extent  of  Aftonian  sand  (continuous  with  the  Aftonian  sand 
found  in  all  the  river  valleys  of  the  county)  is  close  to  the  surface  in 
the  low  terrace  generally  extensively  devoted  to  the  cultivation  of  water- 
melons. At  one  point  the  sands  have  been  excavated  for  railroad 
ballast.  Across  Allen,  Richland,  and  Union  townships  are  other  numer- 
ous exposures,  the  most  noteworthy  of  which  are  in  Section  24  of  Rich- 


THE   AFTONIAN   INTERGLACIAL  DEPOSITS  23 

land  Township  (S.E.  J  of  the  N.E.  J)  and  the  northeastern  part  of  Section 
3  of  Union  Township  (S.E.  J  of  the  N.E.  J).  While  these  sands  rest  in 
part  on  the  Carboniferous  and  in  part  upon  a  sub-Aftonian  drift  which, 
so  far  as  there  is  evidence,  is  thin,  the  surface  of  these  extensive  tracts 
of  sand  generally  grades  up  into  the  loess  without  an  intervening  Kansan 
drift,  but  Kansan  drift  is  found  on  the  hillsides,  and  in  some  places  about 
the  sand. 


AFTONIAN  SAND 

In  Section  28  of  Richiand  Township  (S.E.  £  of  the  N.E.  £)  are  the  thickest  deposits 
of  Aftonian  sand  to  be  seen  in  the  county,  about  twenty-three  feet  appearing  both 
in  the  road  and  in  the  ravine  near  the  top  of  the  hill.  The  direction  of  the  view  is 
southeast.  The  thick  stratum  near  the  bottom  of  the  picture  is  No.  5  of  the  descrip- 
tion in  the  text. 


The  deposit  in  Section  24  of  Richiand  Township  is  the  thickest 
deposit  of  Aftonian  sand  to  be  seen  in  the  county.  The  deposit  as  a 
whole  presents  characteristics  that  are  similar  to  what  is  found  north- 
east of  New  Virginia.  The  lower  portion  has  various  bands  of  sand 
stained  with  oxide  of  iron,  alternating  with  unstained  portions  and 
with  other  portions  containing  an  admixture  of  black  dust.  The  upper 
portions  are  free  from  these  alternations. 


PLEISTOCENE   DEPOSITS   IN   WARREN   COUNTY,    IOWA 


Feet 

2 


Inches 

3 


10 


No. 


Loess,  sandy  in  principal  part  of  exposure,  clayey  farther 
east;   grading  from  sand  up  into  loess  in  an  excavation  at 
a  house  close  by  on  the  opposite  side  of  the  road. 
Sand,  fine,  light  colored,  horizontal. 

Sand,  fine  in  places,  cross-bedded  in  eastern  part  of  expo- 
sure, beds  dipping  southeast;  horizontal  in  western  part. 
Sand,     fine,     gray,     closely    compacted,    and    somewhat 
cemented. 

Sand,  fine,  upper  three  inches  red,  with  half  an  inch  of 
black  included:   alternating  red  and  gray  below. 
Sand,  fine,  black  and  gray  above,  reddish  brown  below. 
Sand,  fine,  brownish  gray,  horizontally  bedded. 
Not  exposed. 

Section  of  Af  tonian  sand,  Section  24  of  Richland  Township 
(S.E.  i  o!  the  N.E.  1). 


AFTONIAN  SAND 

The  location  is  the  same  as  that  given  in  the  preceding  illustration,  but  the  direc- 
tion of  view  is  east.     Stratum  No.  5  is  near  the  middle  of  the  picture. 


All  of  the  strata  are  of  fine  sand.     The  very  evident  lamination 
(in  Nos.  2  and  4)  is  not  due  to  marked  difference  in  the  size  of  the  sand 


THE   AFTONIAN   INTERGLACIAL  DEPOSITS  25 

grains  but  to  the  difference  in  the  color  of  the  material  along  with  the 
sand.  The  layers  of  dark  material  are  not  layers  of  soil  formed  in  situ, 
but  of  dark  material  deposited  by  the  wind,  as  dust  deposited  by  the 
wind  may  now  be  seen  by  the  roadside,  only  in  this  ravine  the  dust  is 
more  sandy  than  that  ordinarily  found  by  the  roadside.  All  is  closely 
compacted.  No.  5  breaks  away  in  large  blocks  that  roll  to  the  bottom 


AFTONIAN  SAND 

Aftonian  sand  outcropping  in  a  road  that  had  not  been  recently  worked. 
N.E.  I  of  the  N.W.  J  of  Section  27,  Allen  Township.) 


(The 


of  the  ravine.  No.  6  is  not  cross-bedded  in  the  direction  of  the  slope 
of  the  hill,  nor  in  the  direction  of  the  drainage  of  the  larger  ravine  of 
which  this  smaller  ravine  is  a  branch,  but  in  the  opposite  direction,  the 
southeast,  the  direction  of  transportation  by  a  prevailing  wind  blowing 
from  the  northwest  across  the  heavy  deposits  of  sand  near  the  mouths 
of  North  and  Middle  rivers  and  along  the  valley  of  the  Des  Moines. 
While  this  is  the  direction  in  which  the  Des  Moines  River  flows,  the 
deposit  is  on  the  edge  of  the  upland,  above  the  level  of  the  sand  found 
near  Avon.  The  Kansan  drift  is  above  it  to  the  north,  east,  and  south. 


26  PLEISTOCENE   DEPOSITS   IN   WARREN   COUNTY,    IOWA 

Two  miles  south  of  Indianola  (S.W.  J  of  the  S.W.  J  of  Section  6, 
Otter  Township)  a  deposit  of  sand  at  least  six  feet  thick  was  exposed  at 
one  time  in  the  side  of  the  river  trench,  the  surface  of  the  deposit  lying 
about  four  feet  below  the  surface  of  the  bottom  land  and  about  twelve 
feet  above  low  water  in  the  river.  Between  the  railroad  bridge  and  the 
wagon  bridge  south  of  Ackworth  sand  lies  on  the  sub-Aftonian  drift 
about  six  feet  above  the  usual  level  of  low  water  in  the  stream  and 
extends  south  as  a  considerable  deposit  in  the  side  of  the  hill.  South- 
east of  Milo  it  forms  a  bed  eight  feet  thick  on  the  hillside  in  the  south- 
eastern quarter  of  Section  27  (Belmont  Township)  and  supplies  the  larger 
part  of  the  sand  washed  into  ravines  to  the  south.  In  White  Breast 
Township  it  forms  a  conspicuous  deposit  at  the  church  and  cemetery 
(Section  36),  where  it  overlies  the  sub-Aftonian  drift  at  about  the  middle 
of  the  west  slope  of  the  hill  and  is  overlain  by  a  thin  deposit  of  Kansan 
drift  in  the  cemetery.  The  relation  of  all  these  deposits  beneath  near-by 
Kansan  and  above  sub-Aftonian  drift  marks  them  as  Aftonian. 

Along  all  the  rivers  it  forms  a  continuous  deposit  extending  a  few 
feet  beneath  the  beds  of  the  streams,  evidently  marking  the  lowest  lines 
to  which  Aftonian  erosion  proceeded.  With  the  aid  of  an  over-deposit 
of  later  material  it  forms  the  low  terrace  along  the  rivers,  best  developed 
near  Avon.  Tongues  of  sand  now  extend  from  the  upland  down  beneath 
the  present  soil  of  the  large  ravines  to  the  sand  of  the  river  valleys. 

FOSSILS1   FROM   THE   AFTONIAN 

In  five  well  records  wood  is  described  as  with  the  gravel  or  with  sand 
closely  associated  with  the  gravel.  In  four  places  bones  of  animals 
were  discovered:  At  Avon  several  years  ago_workmen  in  the  gravel  pit 
unearthed  a  tusk  and  several  large  bones  thought  to  be  of  a  mastodon 
(reported  by  Mr.  John  O.  Baker,  engineer),  and  later,  fragments  of 
other  animals  (reported  by  Mr.  William  T.  Rich,  conductor).  One  of 
these  bones  was  a  metapodial  of  some  animal  like  a  buffalo  or  ox,  and 
one  a  vertebra  which  is  thought  to  be  of  a  deer.  In  Section  20  of  Rich- 
land  Township  Mr.  F.  H.  Stack  while  digging  a  well  found  at  the  bottom 
of  it  a  bone  four  inches  long  which  he  thought  came  from  the  foot  of 
some  animal  like  a  wolf,  and  sticks  of  brush  that  had  been  burned,  a 

1  The  "Aftonian  Mammalian  Fauna"  is  described  by  Professor  Calvin  in  Bulletin 
of  the  Geological  Society  of  America,  Vol.  XX,  pp.  341-56. 

On  the  identification  of  plants  found  in  Aftonian  peat  see  T.  H.  Macbride,  "A 
Pre-Kansan  Peat  Bed,"  Proceedings  of  the  Iowa  Academy  of  Sciences,  Vol.  IV  (1896), 
pp.  63-66;  and  T.  E.  Savage,  "A  Buried  Peat  Bed  in  Dodge  Township,  Union  County, 
Iowa,"  ibid.,  Vol.  XI  (1903),  pp.  103-9. 


THE   AFTONIAN   INTERGLACIAL  DEPOSITS  2J 

part  having  been  converted  into  charcoal.  From  Section  29  of  Lincoln 
and  Palmyra  .townships  Mr.  Herbert  D.  Perry  brought  in  three  speci- 
mens all  of  which  are  broken  and  worn.  One  is  a  first  vertebra  (atlas) 
five  and  three-fourths  inches  across;  another,  a  lumbar  vertebra  5X4^ 
inches  across  and  2\  inches  thick.  These  were  found  ten  or  twelve  feet 
from  the  surface  in  a  ravine  where  digging  was  in  process  for  a  bridge 
pier.  In  Section  19  of  Liberty  Township  ten  feet  below  the  upland  Mr. 
George  Leeper  in  digging  .a  well  came  across  a  thigh  bone  3  to  3^  feet 
long,  and  a  rib. 

None  of  these  specimens  have  been  seen  by  the  writer  excepting 
those  brought  in  by  Mr.  Rich  and  by  Mr.  Perry,  all  of  which  are  now 
deposited  in  the  museum  of  Simpson  College.  Those  brought  by  Mr. 
Rich  were  sent  to  the  University  of  Iowa  for  identification. 

THE  SOURCE  OF  THE  MATERIAL 

Undoubtedly  a  considerable  proportion,  if  not  the  larger  part,  of 
the  Aftonian  sands  and  gravels  found  away  from  the  river  valleys  was 
washed  out  of  the  sub- Aftonian  drift.  That  pebbles  of  the  size  of  some 
of  those  found  near  Afton  Junction  did  lie  in  the  sub-Aftonian  drift  is 
evident  from  an  occasional  pebble  and  cobble  found  in  it  now,  and 
evident  also  from  the  gravel  found  at  the  bottom  of  twenty-five  feet  of 
Aftonian  in  the  college  well.  Much  of  the  sand  and  gravel  generally  in  the 
county  is  so  coarse  and  so  bedded  as  to  preclude  the  possibility  of  any 
agency  except  that  of  water,  which  must  have  transported  away  the  finer 
material  and  redeposited  the  coarser  during  the  general  progress  of  the 
erosion  of  valleys  in  the  sub-Aftonian.  Such  material  could  not  have 
been  left  in  its  present  position  by  wash  from  a  receding  sub-Aftonian 
ice  sheet,  for  the  sands  and  gravels  lie  along  valleys  eroded  in  various 
directions  in  the  sub-Aftonian,  and  not  along  lines  which  extend  across 
the  county  north  and  south,  independently  of  the  present  general 
lines  of  erosion.  For  the  same  reason  they  could  not  have  been  deposited 
in  their  present  relation  by  water  from  an  advancing  Kansan  ice.  The 
later  ice  sheet  known  as  the  Wisconsin  could  scarcely  have  interfered 
seriously  with  the  drainage  from  the  county,  for  that  ice  sheet  did  not 
push  south  of  Des  Moines,  and  the  chief  drainage  line  between  the 
Wisconsin  ice  sheet  and  Warren  County  (the  Des  Moines  River  south 
of  Des  Moines)  had  already  been  established. 

The  twenty-five  feet  of  old-soil-like  material  found  over  the  gravel 
in  the  Simpson  College  well  is  of  such  a  character  as  to  suggest  deriva- 
tion from  the  sub-Aftonian  clay,  perhaps  by  gradual  wash  from  higher 


28  PLEISTOCENE   DEPOSITS   IN   WARREN   COUNTY,    IOWA 

ground  and  deposition  on  lower  ground,  much  as  at  the  present  day 
the  soil  is  gradually  washed  from  the  higher  slopes  to  the  lower  ones 
where  in  places  it  forms  deposits  as  much  as  six  feet  thick  of  a  rich  black 
loam.  The  several  thin  layers  of  peatlike  growth  suggest  that  the 
deposit  may  have  been  formed  in  that  portion  of  Aftonian  time  in  which 
the  thicker  peat  beds  found  near  Oelwein  and  Tama  were  formed.  It 
is  apparently  to  this  same  horizon  that  the  gas-producing  well  in  Madi- 
son County,  about  three  miles  west  of  Church ville,  belongs. 

The  fine  sand  in  thin  bands  in  the  old-soil-like  deposit  and  also 
scattered  through  the  other  portions  of  it,  the  fineness  of  some  of  the 
other  deposits,  the  position  of  beds  of  fine  sand  at  least  associated  with 
Aftonian  along  the  brows  of  hills  south  of  each  of  the  rivers  and  on  hill- 
tops where  there  is  no  evident  source  for  the  sand  by  water  erosion  and 
deposition,  and  the  cross-bedding  noted  (Section  24  of  Richland  Town- 
ship), opposite  to  drainage  but  coinciding  with  the  direction  of  a  pre- 
vailing wind,  suggest  the  possibility  of  local  eolian  action;  but  such  an 
interpretation  seems  out  of  harmony  with  descriptions  of  Aftonian 
deposits  in  other  places  where  the  deposits  are  not  in  the  least  of  eolian 
origin. 

It  should  be  noted  that  the  sequence  of  deposits  in  the  Simpson 
College  well  coincides  with  the  general  relation  of  a  coarser  lower  por- 
tion to  a  finer  upper  portion  found  in  various  parts  of  the  county;  and 
indicates  that  a  time  of  marked  erosion,  accompanied  by  re-deposition 
of  the  gravel,  was  followed  by  a  time  of  marked  deposition  in  which  the 
old-soil-like  material  in  the  well  was  deposited,  and  possibly  at  the  time 
when  a  portion  of  the  sand  in  other  parts  of  the  county  was  deposited. 
Such  a  relation  of  a  time  of  marked  Aftonian  erosion  followed  by  a  time 
when  the  deeper  portions  of  valleys  were  clogged,  seems  to  represent 
two  marked  divisions  in  Aftonian  time  for  this  part  of  the  country. 

AFTONIAN  RELIEF 

The  greatest  Aftonian  relief  must  have  been  at  a  time  when  the 
trenches  formed  by  erosion  had  reached  the  lowest  levels  of  which  there 
is  now  evidence,  while  at  least  portions  of  the  sub-Aftonian  surface  had 
as  yet  suffered  little  erosion.  The  lowest  level  is  approximately  ten  feet 
below  the  present  stream  beds.  The  highest  elevations  could  not  have 
been  lower  than  the  present  highest  portions  of  the  Carboniferous  and 
the  present  highest  portions  of  the  sub-Aftonian  drift.  How  much 
higher  the  highest  portions  of  the  hills  actually  were  at  the  time  we  can- 
not now  tell,  but  an  estimate  of  the  relief  can  be  made  that  will  be  nearly 


THE   AFTONIAN   INTERGLACIAL   DEPOSITS  2Q 

enough  correct  for  a  fair  comparison  with  the  amount  of  present  relief 
in  the  same  townships.  This  is  obtained  by  adding  to  the  present  relief 
ten  feet  for  the  estimated  depth  of  Aftonian  deposits  below  the  present 
beds  of  the  streams,  and  subtracting  thirty  feet  for  the  average  level  of 
the  sub-Aftonian  hills  below  the  present  level  of  the  upland. 

Feet  Feet 

Linn no  Jackson 1 50 

Greenfield 120  White  Oak 160 

Allen 120  Otter 169 

Richland 166  Belmont 170 

Jefferson 120  Virginia 184 

Lincoln  and  Greenfield . .   143  Squaw 117 

Lincoln  and  Palmyra .  . .   143  Liberty 117 

Union 120  White  Breast 170 

Estimate  of  early  Aftonian  relief  based  on  assumptions  stated  in  the  text. 

While  in  the  later  portions  of  Aftonian  time  the  valleys  were  clogged 
to  about  the  present  level  of  the  river  beds,  the  upper  portions  of  the 
Aftonian  hills  were  probably  still  undergoing  erosion  in  many  places, 
though  the  level  of  the  uplands  would  be  reduced  very  slowly. 

To  obtain  an  estimate  of  the  closing  Aftonian  relief  over  which  the 
Kansan  ice  pushed  its  way,  we  may  subtract  ten  feet  from  the  preceding 
estimate  of  early  Aftonian  relief  for  the  silting-up  of  the  river  valleys, 
and  leave  the  estimated  level  of  the  Aftonian  hills  unchanged. 

Feet  Feet 

Linn 100  Jackson 140 

Greenfield .  .  . '. no  White  Oak 150 

Allen no  Otter 159 

Richland 156  Belmont 160 

Jefferson no  Virginia 174 

Lincoln  and  Greenfield . .  133  Squaw 107 

Lincoln  and  Palmyra. . .  133  Liberty 107 

Union 1 10  White  Breast 160 

Estimate  of  the  closing  Aftonian  relief  based  on  assumptions  stated  in  the 
text. 


THE  KANSAN  DRIFT 

THE   NAME 

The  drift  which  is  uppermost  in  south-central  Iowa,  H.  F.  Bain  has 
traced  southwest  and  found. to  connect  with  the  surface  drift  in  Kansas 
where  it  had  been  known  as  the  Kansan  drift.1 

THE  GENERAL  CHARACTER  OF  THE  KANSAN  DRIFT 

The  clayey  portion  of  the  drift  thus  named  is  of  a  bluish-black  color 
where  not  weathered,  with  fine  sand  and  minute  pebbles  scattered 
through  it.  Though  impervious  enough  where  thick  to  form  a  substratum 
for  the  water  horizon  above  it,  it  is  not  so  tenacious  as  the  sub-Aftonian 
drift,  and  contains  a  larger  admixture  of  sand,  pebbles,  and  bowlders 
than  is  found  in  the  sub-Aftonian.  The  surface  weathers  into  a 
yellow  clay,  the  yellow  color  being  apparently  due  to  the  oxidation  and 
hydration  of  the  iron  which  the  clay  contains.  The  general  character 
of  the  clay,  the  variation  in  it  from  its  surface  down,  and  the  way  it 
weathers  along  cracks,  may  be  found  minutely  described  in  a  preceding 
chapter  on  the  record  of  the  Simpson  College  well.  It  is  along  these 
cracks  that  sand  sifts  in  from  above,  forming  passage  ways  through 
which  water  from  above  can  percolate  to  the  Aftonian  below  where  the 
Kansan  is  thin. 

The  distance  from  the  surface  of  the  Kansan  that  effervescence 
begins  is  variable.  Where  the  Kansan  is  thin  and  rain  water  has  oppor- 
tunity to  soak  down  through  it  and  away,  the  drift  is  thoroughly 
weathered  and  does  not  now  effervesce  at  all.  Where  ascending  waters 
bring  lime  even  the  weathered  portions  of  the  drift  may  effervesce  clear 
to  the  surface,  as  at  a  point  half  a  mile  east  of  New  Virginia  near  a  lime- 
stone region.  Here  cracks  in  the  clay  near  by  are  lined  and  even  filled 
with  calcium  carbonate  brought  by  water  moving  horizontally  and 
vertically.  At  the  college  well  effervescence  begins  at  the  top  of  the 
unweathered  portion  three  feet  below  the  surface  of  the  Kansan  and 
continues  to  the  base  of  the  Kansan.  It  is  not  known  how  much  of 
weathered  Kansan  may  have  been  eroded  away,  but  at  present  leaching 

1  H.  F.  Bain,  "Relation  of  the  Wisconsin  and  Kansas  Drift  Sheets  in  Central 
Iowa,  and  Related  Phenomena,"  Iowa  Geological  Survey,  Vol.  VI,  p.  464;  also  T.  C. 
Chamberlin,  "The  Classification  of  American  Glacial  Deposits,"  Journal  of  Geology, 
Vol.  Ill,  p.  271. 

30 


THE    KANSAN  DRIFT  31 

is  not  favored  at  this  point.     Here  percolation  downward  through  the 
Kansan  is  impossible  and  lateral  movement  is  slow. 

The  pebbles  and  bowlders  in  the  Kansan  are  of  all  sizes  up  to  three 
and  four  feet  in  diameter.  These  very  resistant  bowlders  are  of  light- 
colored  granite,  red  quartzite,  and  greenstone,  but  the  largest  bowlders 
found  are  granites  and  red  quartzites,  not  greenstones.  Among  the 
bowlders  are  dark  granites  which  are  soft  through  decomposition  of 
ferromagnesian  minerals.  Where  observed  these  lie  in  the  weathered 
portion  of  the  Kansan.  The  accompanying  table  will  serve  to  illustrate 
a  grouping  of  pebbles  that  may  be  found : 

Granite,  not  decomposed 39 

Granite,  decomposed 2 

Quartzite,  red 13 

Quartzite,  white 9 

Quartz 2 

Greenstone 22 

Chert i 

Hornblende  schist  and  other  hornblende  rocks 

not  granite 2 

Sandstone,  foreign .  . 4 

Sandstone,  local 5 

Limestone i 

100 

Table  of  percentages  of  the  different  kinds  of  rocks  among  the  pebbles 
of  the  Kansan  drift  found  just  south  of  the  fairgrounds  at  Indianola  (S.E.  |  of 
the  S.E.  \  of  Section  26,  Lincoln  and  Greenfield  townships). 

It  is  not  possible  to  compare  the  distribution  of  pebbles  in  Warren 
County  with  the  distribution  in  counties  to  the  north  and  to  the  south 
since  no  records  as  to  the  distribution  are  to  be  found  for  counties  in 
these  directions;  but  the  records  prepared  by  Professor  J.  A.  Udden 
give  opportunity  to  compare  the  percentages  of  the  different  kinds  of 
rocks  among  the  pebbles  of  the  Kansan  drift  of  Warren  County  with 
the  percentages  found  in  the  eastern  and  in  the  western  parts  of  the 
state.1 

Omitting  the  sandstone,  limestone,  and  dolomite,  all  of  which  are 
here  treated  as  of  local  origin,  and  reducing  the  remainder  to  a  common 

1  For  the  eastern  part  of  the  state:  J.  A.  Udden,  "Geology  of  Clinton  County," 
Iowa  Geological  Survey,  Vol.  XV,  p.  417;  "Geology  of  Muscatine  County,"  ibid., 
Vol.  IX,  p.  316;  "Geology  of  Jefferson  County,"  ibid.,  Vol.  XII,  p.  427. 

For  the  western  part  of  the  state:  J.  A.  Udden,  "Geology  of  Pottawattamie 
County,"  ibid.,  Vol.  XI,  p.  253.  In  this  last  report  Professor  Udden  compares  the 
percentages  of  pebbles  taken  from  the  lower,  middle,  and  upper  portions  of  the  Kansan. 


32 


PLEISTOCENE   DEPOSITS   IN   WARREN    COUNTY     IOWA 


basis  of  100  per  cent,  the  records  of  foreign  pebbles  from  one  to  three 
inches  in  diameter  are  given  in  the  accompanying  table. 

LOCAL  MATERIAL  OMITTED 

COMPARISON  OF  THE  PERCENTAGES  OF  DIFFERENT  KINDS  OF  ROCKS  NOT  LOCAL 
FOUND  AMONG  THE  PEBBLES  OF  THE  KANSAN  DRIFT  IN  WARREN  COUNTY 
WITH  THE  PERCENTAGES  FOUND  IN  THE  EASTERN  AND  WESTERN  PARTS  OF 
THE  STATE 


Eastern. 
Average  of 
i,  2,  and  3 

Central. 
Warren  County 

Western. 
Pottawattamie 
County 

Granite  

27.  5 

45  •  6 

25.  7 

Quartzite,  red  and  purple  

9-  J 

14.5 

4.3 

Ouartzite  white 

o  o 

10  o 

7      Q 

Quartz 

e   6 

2    2 

r    A 

Greenstone  (largely  diabase) 

41  6 

24   4 

37    2 

Chert 

8  3 

I  .  I 

II  .^ 

Hornblende  schist                               .... 

1.8 

2  .  2 

I  -0 

Jasper    .        .  .      .                 

o.o 

O.O 

O.  2 

Other  kinds  of  rocks  

6.0 

O.O 

8.7 

99-9 

100.  0 

98.8 

No.  i,  Clinton  County;   No.  2,  Muscatine  County;   No.  3,  Jefferson  County. 

According  to  this  table  the  granites  are  more  abundant  in  the  center 
than  in  either  the  eastern  or  the  western  portions  of  the  state,  but  from 
other  records  not  here  given  they  are  distributed  somewhat  uniformly. 
Counting  the  purple  quartzites  with  the  red,  since  in  other  counties  than 
Warren  the  purple  quartzites  are  not  mentioned  separately,  these  colored 
quartzites  are  found  to  be  more  numerous  in  the  central  part  of  the  state 
(Warren  County)  than  in  either  the  eastern  or  the  western  parts  of  the 
state.  A  comparison  of  the  quartz  and  white  quartzites  does  not  seem 
advisable.  Many  of  the  stones  that  seem  to  the  naked  eye  to  be  quartz 
are  found  when  examined  under  a  magnifier  to  be  completely  cemented 
quartzites.  The  greenstones  are  less  abundant  in  Warren  County 
than  in  either  the  eastern  or  the  western  parts  of  the  state.  The  chert  is 
more  abundant  in  the  western  part  of  the  state  than  in  the  eastern 
part  of  it.  At  the  point  selected  in  Warren  County  the  chert  is  less 
abundant  than  in  either  the  eastern  or  the  western  part,  but  at  other 
points  in  Warren  County  the  chert  is  even  more  abundant  than  in  the 
western  part  of  the  state. 

Whether  such  comparisons  express  general  relations  through  the 
state  cannot  now  be  ascertained.  They  may  serve  as  an  aid  in  tracing 
the  Kansan  bowlders  back  to  their  original  sources.  For  this  purpose 


THE   KANSAN  DRIFT  33 

certain  of  the  bowlders  seem  more  suitable  than  the  others.  The 
pieces  of  copper,1  at  least  three  of  which  have  been  found  in  Warren 
County,  and  other  pieces  reported  from  other  counties,  seem  to  be  the 
best  except  that  they  are  rare.  Other  distinctive  rocks  are  the  red 
and  purple  quartzites;  also  hematite,  none  of  which  happened  to  be 
among  the  pebbles  here  listed. 

THE   KANSAN   DRIFT   CONTRASTED   WITH   THE    SUB-AFTONIAN   DRIFT   IN 
COMPOSITION  AND   TOPOGRAPHY 

The  Kansan  drift  differs  from  the  sub-Af tonian  drift  in  the  presence 
in  the  Kansan  of  a  larger  proportion  of  grit,  pebbles,  and  bowlders. 
The  Kansan  weathers  from  a  blue  to  a  yellow,  while  the  sub-Aftonian 
often  presents  a  dark  appearance  close  beneath  the  wash  of  iron  oxide 
that  often  covers  its  surface,  and,  where  weathered,  weathers  into  a 
brown  clay  of  the  same  tenacious  character  as  that  of  the  unweathered 
mass.  The  characteristic  bowlders  of  the  Kansan  are  red  quartzite 
and  greenstone  together  with  dark  decomposing  granites,  while  character- 
istic pebbles  of  the  sub-Aftonian  are  light  granites  and  white  quartz. 
It  is  noted  that  the  abundance  of  grit,  pebbles,  and  bowlders  in  the 
Kansan  is  due  not  alone  to  the  transportation  of  such  material  from  a 
distance  but  also  and  probably  largely  to  the  incorporation  of  the  sands, 
gravel,  and  bowlders  found  on  the  surface  of  the  sub-Aftonian  as  the 
Kansan  ice  pushed  its  way  southward. 

The  topography  is  also  different  in  the  portions  of  the  county  where 
the  Kansan  is  found  to  be  thick  and  the  sub-Aftonian  not  conspicuous, 
from  the  topography  where  the  Kansan  is  thin  and  the  sub-Aftonian 
deeply  eroded.  Where  the  Kansan  is  thick  the  Aftonian  valleys  are  still 
wholly  or  partially  rilled  with  Kansan  not  yet  eroded,  and  the  hillsides 
wash  easily  so  that  the  hills  are  not  so  steep  sided  as  where  the  Kansan 
is  thin  and  the  sub-Aftonian  deeply  exposed.  Other  factors  than 

1  If  the  copper  came  from  the  Lake  Superior  region  it  must  have  first  been 
transported  west  or  southwest  by  an  earlier  ice  sheet  (Jerseyan  ?)  so  that  the  Kansan 
ice  was  able  to  secure  it  and  transport  it  south  or  southeast  to  Warren  County.  This 
raises  a  question  as  to  the  exact  contemporaneity  of  the  earliest  known  Labradorean 
and  Keewatin  ice  sheets.  If  the  copper  was  not  first  transported  westward  then  it 
is  possible  undiscovered  deposits  of  copper  have  existed  and  may  still  exist  somewhere 
northwest  of  Warren  County  toward  the  Keewatin  region. 

No  striae  have  been  found  in  the  county,  but  at  Peru,  in  the  eastern  part  of 
Madison  County,  striae  are  reported  to  extend  N.  27°  W.:  F.  A.  Brown,  "A  Contri- 
bution to  Madison  County  Geology,"  Proceedings  of  the  Iowa  Academy  of  Sciences, 
Vol.  XIII  (1906),  p.  204.  Whether  the  striae  were  caused  by  Kansan  or  by  sub- 
Aftonian  ice  is  not  discussed. 


34  PLEISTOCENE   DEPOSITS   IN   WARREN   COUNTY,    IOWA 

difference  in  structure  of  these  two  deposits  are,  however,  involved; 
for,  on  the  south-facing  surfaces  of  the  river  valleys  the  sub-Aftonian 
drift,  like  later  deposits,  has  been  eroded  to  a  more  gentle  slope  than 
the  north-facing  surfaces;  and  the  drift  itself  may  have  been  deposited 
in  greater  thickness  above  the  preglacial  drainage  lines  in  the  southwest 
parts  of  the  county  than  it  was  in  the  northeast  parts.  The  distance 
from  the  master  stream  of  the  region  (the  Des  Moines  River)  does  not 
seem  to  be  involved,  for  the  difference  in  relief  between  that  of  Richland 
Township,  nearest  the  master  stream  (186  feet),  and  that  of  Virginia 
Township,  farthest  from  the  master  stream  (204  feet),  does  not  seem 
sufficient  to  account  for  the  difference  in  topography.  If  the  total  fall 
in  the  upland  surface  (about  188  feet)  be  compared  with  the  total  fall 
along  the  bed  of  South  River  (186  feet),  the  difference  is  very  slight 
indeed  (two  feet).  Neither  is  the  difference  in  the  resistance  of  the 
Missourian  limestone  as  compared  with  the  resistance  of  the  Des  Moines 
shales  and  sandstone  involved,  for  this  difference  in  topography  is  noted 
in  townships  both  to  the  north  and  to  the  east  of  Virginia  Township  in 
which  the  Missourian  limestone  is  not  found. 

Both  where  the  Kansan  is  thin  and  where  it  is  thick  the  entire  upland 
surface  is  completely  drained,  no  natural  ponds  whatever  remaining 
outside  of  the  river  bottoms. 

THE    KANSAN   DRIFT   CONTRASTED   WITH   THE   WISCONSIN   DRIFT   IN 
COMPOSITION   AND   TOPOGRAPHY 

The  Kansan  drift  differs  from  the  Wisconsin  drift,  the  nearest  over- 
lying drift  to  the  north,  in  the  amount  of  stratified  sand  and  gravel  con- 
tained. The  Kansan  contains  comparatively  few  masses  of  sand;  such 
as  have  been  found  are  bowlders  of  Aftonian  sand  included  in  the  lower 
portion  of  the  Kansan.  The  Wisconsin  drift  contains  a  considerable 
amount  of  stratified  sand  and  gravel.1  The  surface  of  the  Kansan  is 
weathered  to  a  much  greater  extent  than  the  surface  of  the  Wisconsin. 

Weathered  bowlders  are  common  in  the  Kansan,  especially  in  the 
upper  portions  of  it.  Among  these  are  the  dark  granites  that  can  be 
crushed  in  the  hand.  The  bowlders  of  the  Wisconsin  drift  are  in  general 
comparatively  unweathered. 

In  topography  the  area  where  the  Kansan  drift  is  at  the  surface 
stands  in  marked  contrast  to  the  area  where  the  Wisconsin  drift  is  at  the 

1  S.  W.  Beyer,  "Geology  of  Boone  County,"  Iowa  Geological  Survey,  Vol.  V,  p. 
304;  "  Geology  of  Carroll  County,"  ibid.,  Vol.  IX,  p.  94;  "  Geology  of  Story  County," 
ibid.,  Vol.  IX,  p.  203;  H.  F.  Bain,  "Geology  of  Polk  County,"  ibid.,  Vol.  VII,  p.  344. 


THE   KANSAN   DRIFT  35 

surface.  On  the  Kansan  upland  the  drainage  is  complete,  there  being 
no  swamps  nor  ponds.  The  topography  is  somewhat  past  maturity. 
On  the  Wisconsin  there  are  undrained  swamps  and  ponds  occupying 
the  depressions  of  a  gently  undulating  surface  varied  by  a  few  kames  and 
gravel  trains1 — a  youthful  glacial  topography. 

THE   DISTRIBUTION  AND   THICKNESS    OF   THE   KANSAN   DRIFT 

The  weathered  phase  of  the  Kansan  is  found  in  the  upland  through- 
out the  county,  along  the  hills  of  which  it  outcrops  in  conspicuous  bands 
of  yellow  claty  mixed  with  sand,  bowlders,  and  pebbles.  In  the  west 
range  of  townships  it  forms  a  veneering  apparently  thin  over  the  tops 
of  the  Aftonian,  covering  hills  of  sub-Aftonian  drift.  Along  the  southern 
tier  of  townships  it  supplies  material  for  the  gravelly  noses  of  divides. 
In  the  rest  of  the  county  generally  it  forms  conspicuous  bands  of  yellow 
clay  mixed  with  sand,  bowlders,  and  pebbles  and  stained  by  an  oxide 
of  iron.  It  is  at  this  horizon  that  the  large  bowlders  appear  here  and 
there  in  the  fields.  Much  of  the  Kansan  is  so  thin  as  to  be  completely 
weathered,  simply  mantling  an  Aftonian  topography.  Well  records 
obtainable  are  not  generally  sufficiently  detailed  to  make  it  clear  just 
what  is  Kansan  and  what  is  sub-Aftonian,  but  from  the  character  of 
the  clay  found  in  the  deeper  ravines  it  appears  that  the  deep-lying  clay 
in  the  preglacial  valleys  throughout  the  county  is  sub-Aftonian  and  not 
Kansan,  especially  in  the  western  portion  of  the  county;  but  it  is  clear 
that  Kansan  drift  fills  some  of  the  minor  Aftonian  valleys,  for  at  the 
Simpson  College  well  the  Kansan  drift  is  fifty-seven  feet  thick,  conceal- 
ing a  valley  of  which  there  is  no  evidence  whatever  in  the  present  topog- 
raphy. On  present  evidence  the  thickness  of  the  Kansan  varies  from 
o  to  75  feet  with  an  average  that  cannot  be  stated,  though  from  rela- 
tions in  the  county  generally  it  appears  to  be  nearer  one-third  of  the 
maximum  thickness  found  than  it  is  two-thirds  of  that  thickness. 
From  the  upland  it  frequently  extends  down  the  sides  of  ravines.  Along 
the  deeper  ravines  it  is  frequently  wanting,  so  that  one  may  follow  the 
exposures  of  sub-Aftonian  from  the  deeper-lying  portions  and  trace  it 
without  a  change  to  the  dark  clay  beneath  the  washed  soil  in  the  shal- 
lower upper  portions  of  the  ravine,  as  in  ravines  between  Liberty  Center 
and  Lacona,  and  one  ravine  south  of  Churchville.  In  the  two  ravines 
mentioned  it  appears  that  the  Kansan  may  never  have  been  present, 
for  there  are  no  traces  of  bowlders  and  pebbles  that  would  have  been 

1  Personal  observation;   also  H.  F.  Bain,  "Geology  of  Polk  County,"  Iowa  Geo- 
logical Survey,  Vol.  VII,  pp.  344-50. 


36  PLEISTOCENE  DEPOSITS  IN  WARREN  COUNTY,   IOWA 

left  if  the  clay,  sand,  and  smaller  pebbles  had  been  washed  away,  nor  is 
there  any  stratified  sand  and  gravel  visible  in  the  washed  soil  near  the 
trenches.  The  clay  presents  the  character  of  the  sub-Aftonian  drift. 

In  the  northeastern  half  of  the  county  the  sub-Aftonian  drift  is 
largely  absent  from  Carboniferous  upland,  the  Kansan  resting  directly 
upon  the  underlying  Carboniferous.  In  places  the  Kansan  also  is  absent, 
allowing  the  Carboniferous  to  appear  at  the  surface.  This  is  seen  at 
the  west  edge  of  "The  Quarries"  in  Section  22  of  White  Oak  Township. 

The  Kansan  thus  mantles  the  Aftonian  topography,  concealing  some 
of  the  minor  valleys  but  not  the  larger  ones.  Extending  as  it  does 
irregularly  down  the  sides  of  the  hills  of  sub-Aftonian  drift  with  its 
generally  slight  covering  of  Aftonian,  and  outcropping  at  various  inter- 
vals, it  presents  a  deceitful  appearance  of  greater  thickness  than  it 
really  has,  and  conceals  the  sub-Aftonian  drift. 


THE  POST-KANSAN  DEPOSITS 

THE  POST-KANSAN  DEPOSITS  FOUND  IN  THE  SIMPSON  COLLEGE  WELL,  AND 
THE  RELATION  OF   SUCH  DEPOSITS  THROUGHOUT  THE   COUNTY 

In  the  previous  chapter  on  the  record  of  the  Simpson  College  well 
may  be  found  a  minute  description  of  the  material  that  is  post-Kansan. 
In  that  description  the  following  sub-divisions  should  be  noted: 

a)  2  ft.   Soil,  a  black  loam  (loess  and  humus). 

b)  12  ft.   Loam,  the  subsoil,  brownish,  porous,  a  mixture  of  clay  and  micro- 

scopic particles  of  quartz,  streaked  with  brownish  oxide  of  iron  in 
rootlike  tubes  and  with  very  thin  layers  of  a  dark-brownish  sand; 
entirely  free  from  pebbles. 

c)  6  ft.   The  upper  three  feet  grading  from  the  loam  above  into  a  dense  blue 

clayey  deposit  below  free  from  sand  and  pebbles  and  impervious  to 
water  (3  feet). 

d)  10  ft.   Light  grayish  blue  for  eight  feet,  with  more  grit  in  the  upper  portion 

than  in  the  more  impervious  deposit  above  and  with  traces  of  a 
brown  oxide  of  iron. 

The  first  four  feet  of  the  eight  caved  badly,  large  water-soaked 
masses  (wet  from  -below  upward)  scaling  in  vertical  sheets  from  the 
side  of  the  well,  as  the  uppermost  phase  of  the  loess  does  by  the 
roadside.  The  lowest  four  feet  of  the  ten  is  grayish  in  color  and  with 
grayish  and  brown  sand  scattered  through  it. 

In  the  middle  and  lowest  portions  of  this  deposit  two  pebbles  were 
found  (one  at  26  feet  and  one  at  30  feet),  but  each  was  less  than 
half  an  inch  in  diameter. 

e)  2  ft.   Sand,  pure,  brown  and  gray,  varying  in  thickness  from  o  to  4  feet 

in  wells  located  a  few  feet  from  each  other. 

32ft. 

The  deposit  as  a  whole  corresponds  to  that  which  is  commonly 
found  throughout  the  upland  in  the  central  portion  of  the  county  and 
at  places  even  in  lower  ground.  The  black  soil  here  found  is  of  average 
thickness.  In  the  county  as  a  whole  it  varies  from  o  thickness,  where 
recent  erosion  is  pronounced  upon  the  hillsides,  to  four  and  even  more 
feet  in  thickness  along  the  lower  slopes  of  hills  and  at  the  heads  of  ravines 
toward  which  a  portion  of  the  soil  has  been  transported.  Along  the 
sides  of  the  hills  the  character  of  the  soil  varies  in  composition,  due  to  the 
admixture  of  sand  and  gravel  washed  out  of  various  deposits.  The 

37 


38  PLEISTOCENE   DEPOSITS   IN   WARREN   COUNTY,    IOWA 

brownish  porous  subsoil  (b)  is  also  like  that  commonly  found  through- 
out the  uplands  and  considered  loess.  The  third  division  (c)  lacks  the 
loose  porous  structure  of  the  loess  above,  so  that  it  forms  a  layer  imper- 
vious to  water.  This  denser  deposit  is  judged  to  be  of  loess  that  has 
settled  in  surface  pools,  much  like  the  deposits  now  found  in  shallow 
depressions  occupied  by  water  along  the  river  bottoms.  The  deposit 


RECENT  EROSION 

A  quarter  of  a  mile  south  of  the  fairgrounds  west  of  Indianola  (S.E.  |  of  the  S.E.  | 
of  Section  26)  a  trench  about  four  feet  deep  was  formed  in  two  years  where  there  had 
been  a  wagon  track. 

varies  in  thickness.  It  is  sometimes  found  changed  to  a  yellowish  putty- 
like  layer  over  water  bearing  lower  loess  and  sand.  The  structure  of 
(d)  is  distinctly  that  of  loess,  gray  in  color.  This  deposit  is  also  found  in 
wells  and  in  some  ravines  in  the  central  portion  of  the  county,  both  in 
high  ground  and  in  low  ground.  The  sub-loessial  sand  (e)  at  the  college 
well  is  distinctly  post-Kansan  in  age.  In  other  places  where  the  Kansan 
is  not  present  the  sand  may  be  in  part  Aftonian,  or  where  the  entire 
Pleistocene  deposit  is  now  absent,  may  possibly  even  be  preglacial. 
The  deposit  as  a  whole  mantles  the  Kansan  surface  to  a  depth  of 


THE   POST-KANSAN   DEPOSITS 


39 


from  o  to  30  feet,  maintaining  the  level  character  of  the  divides  and 
sloping  down  the  surface  of  the  larger  ravines  and  the  river  valleys. 
It  is  now  being  trenched  along  all  the  upland  as  the  ravines  work  head- 
ward.  Statements  of  several  of  the  old  settlers,  that  trenches  from  12 


Diagram  of  profile  along  the  ravine  from  Indianola  to  Somerset 


A  profile  of  the  trench  of  a  ravine  from  South  River  north  to  the  fairgrounds  at 
Indianola,  thence  down  the  trench  of  another  ravine  to  Middle  River,  a  total  distance 
in  a  straight  line  of  five  and  a  half  miles,  but  made  seven  miles  by  the  windings  of  the 
trenches  in  the  lower  halves  of  their  valleys.  The  change  in  grade  at  A  is  in  part 
artificial.  At  B  and  C  there  is  rapid  headward  erosion.  At  D  there  is  a  rapid  fall 
of  a  few  feet  due  to  a  thin  layer  of  Carboniferous  limestone  which  offers  more  resistance 
to  erosion  than  is  encountered  in  other  parts  of  the  trench.  There  are  a  few  minor 
changes  in  grade  too  small  to  be  represented  in  the  diagram.  The  flood  plain  is  evi- 
dent for  about  half  the  length  of  each  ravine.  Note  the  unsymmetrical  position  of 
the  divide. 

For  this  profile  I  am  indebted  to  Messrs.  Fred  H.  Osborn  and  Leonard  P.  Dove, 
members  of  a  class  in  geology  under  the  instruction  of  the  writer.  The  differences  in 
elevation  were  obtained  with  a  Y-level  and  the  distances  by  pacing.  The  series  was 
then  connected  with  the  known  elevation  of  the  Chicago,  Burlington  and  Quincy 
station  at  Indianola. 


to  1 6  feet  deep  have  formed  in  ravines  since  their  boyhood,  together 
with  the  general  appearance  of  the  ravines  and  trenches,  make  it  appear 
that  the  renewal  of  erosion  has  begun  since  the  arrival  of  the  white  man, 
and  is  largely  due  to  the  breaking  of  the  sod  by  cattle,  and  to  cultivation 


PLEISTOCENE  DEPOSITS  IN  WARREN  COUNTY    IOWA 


of  the  hillsides;  and  favored  by  replacement  of  the  tall  slough  and  prairie 
grasses  by  blue  grass.  The  renewal  of  erosion  is  not  referable  to  change 
in  elevation. 

ANALYSES — DISCUSSION 

There  are  at  hand  three  analyses  of  samples  collected  in  the  upland 
half  a  mile  east  of  the  college.  These  will  give  a  chance  to  compare  the 
composition  of  the  loess  just  under  the  soil  at  the  point  (analysis  No.  i) 
with  that  of  the  denser,  yellow  subsoil  about  four  feet  from  the  surface 
(analysis  No.  2),'  and  also  with  that  of  the  blue  phase  of  the  deposit 
obtained  about  twenty  feet  from  the  surface  (analysis  No.  3). 

ANALYSES  OF  LOESS* 


No.  i 

No.  2 

No.  3 

Hygroscopic  water  

i  .  70 

1    76 

8  08 

Combined  water  

•2  .  -2-2 

6  80 

c  48t 

Silica  (SiO2)  

72  .  24 

63.    ^I 

66   770 

Alumina  (A12O3)  

1  2.58 

16.  ^i 

IO    CT2^ 

Iron  oxide  as  Fe2O3 

402 

4   06 

O    72 

Manganese  oxide  (MnO) 

o  oo 

O   4Q 

Lime  (CaO) 

I    4O 

I    II 

trace 

Magnesia  (MgO) 

O   OO 

I    IO 

Soda  (Na2O) 

w.yy 
2    OO 

2    2O 

Potash  (KaO) 

I     fA 

o  06 

100.40 

100.39 

100.584 

*  Samples  No.  i  and  No.  2  were  collected  by  the  writer  and  analyzed  by  Professor  G.  E.  Patrick. 
The  analyses  were  published  in  the  "Geology  of  Warren  County,"  Iowa  Geological  Survey,  Vol.  V,  p.  357, 
and  later  republished  in  the  report  on  clays,  Vol.  XIV,  p.  546.  Sample  No.  3  was  collected  and  analyzed 
by  Professor  L.  A.  Youtz  and  published  in  the  Proceedings  of  the  Iowa  Academy  of  Sciences,  Vol.  Ill,  p.  41. 

H.  A.  Wheeler  gives  analyses  of  two  samples  of  "gumbo,"  but  I  do  not  know  whether  the  deposit 
corresponds  to  that  in  Warren  County.  (See  Missouri  Geological  Survey,  Vol.  XI,  p.  118.)  Udden  gives 
a  table  showing  the  percentages  of  different  grades  of  coarseness  in  samples  of  loess  and  gumbo.  (See 
Iowa  Geological  Survey,  Vol.  XI,  p.  257.)  About  5  per  cent  of  the  material  found  in  what  he  calls  gumbo 
is  coarser  than  all  the  material  which  he  found  in  the  loess. 

t  Loss  by  ignition. 

A  comparison  of  these  samples  reveals  a  decrease  in  the  percentage 
of  free  silica  from  the  surface  downward,  an  increase  in  the  percentage 
of  fixed  silica1  accompanied  by  an  increase  in  the  percentage  of  alumina 
(due  to  a  higher  proportion  of  clay)  corresponding  with  the  increase  in 
denseness  which  is  evident  to  the  eye.  The  silica  is  greater  in  the  blue 
phase  (No.  3)  than  in  the  yellow  phase  above  (No.  2).  The  iron  oxide 
is  about  the  same  in  Nos.  i  and  2  but  much  less  in  No.  3.  It  is 
because  the  quantity  of  iron  in  No.  3  is  so  small  that  this  clay  when 

1  The  relation  of  the  silica  is  stated  by  the  chemists. 


THE   POST-KANSAN  DEPOSITS  41 

water  soaked  has  a  light-yellowish  color  instead  of  the  deeper  brownish 
red  as  in  the  yellowish  phase  above,  where  the  iron  is  larger  in  amount. 
The  absence  of  potash,  soda,  magnesia,  lime  (trace),  and  manganese, 
together  with  the  absence  of  iron  (in  No.  3),  makes  it  evident  that  the 
blue  color  is  not  due  to  the  presence  of  undecomposed  dark  ferro- 
magnesian  minerals.  Neither  can  the  blue  color  of  the  blue  clay  be  due 
to  the  presence  of  iron  carbonate,1  for  in  the  locality  named,  at  least,  the 
clay  does  not  effervesce,  nor  do  the  analyses  reveal  the  presence  of  any 
carbonate.  The  loss  by  ignition  in  No.  3  offers  the  only  clue  to  the 
cause  of  the  blue  color.  This  includes  both  the  combined  water  and  the 
organic  material,  the  former  of  which  in  the  process  of  ignition  would 
evaporate  and  the  latter  burn  out.  In  Nos.  i  and  2,  obtained  in  the 
oxidized  and  hydrated  portions  above,  no  organic  matter  was  found. 
In  No.  3  the  loss  by  ignition  was  nearly  as  much  as  in  No.  2,  though  the 
clay  was  denser  and  apparently  equally  exposed  on  the  side  of  the  clay 
pit.  The  loss  seems  largely  due  to  the  ignition  of  the  organic  matter; 
to  which  organic  matter,  therefore,  the  color  of  the  blue  phase  seems 
to  be  due.  The  presence  of  such  organic  matter  would  keep  the  iron 
oxide  in  the  ferrous  state  as  long  as  percolating  surface  water  failed  to 
penetrate  the  deposit.  The  depth  to  this  blue  phase  is  near  the  depth 
to  which  the  rain  water  percolates  vertically  from  the  surface  through 
the  general  body  of  the  loess  where  the  ground  is  level.  It  is  the  depth 
at  which  the  water  was  obtained  (eighteen  to  twenty  feet)  in  shallow 
wells  in  the  upland  prior  to  the  drought  of  1894,  at  which  time  it  became 
universally  necessary  to  sink  all  upland  wells  to  a  depth  of  twenty-eight 
to  thirty  feet. 

1  Iowa  Geological  Survey,  Vol.  XIV,  p.  61,  also  pp.  70-71. 


SUMMARY  OF  TOPOGRAPHIC  HISTORY 

The  topographic  history  above  described  has  recognized: 

1.  A  preglacial  topography  wholly  unlike  that  of  the  present,  with 
drainage  to  which  the  present  lines  do  not  conform,  in  a  country  of 
essentially  horizontal  strata  of  different  degrees  of  resistance  to  erosion 
in  which  a  complete  system  of  drainage  was  developed,  the  valley  lines 
with  preglacial  sand  and  mud  lying  from  45  to  65  feet  below  the  beds 
of  the  present  streams,  and  the  relief  approximately  like  that  of  the 
present. 

2.  A  nearly  complete  obliteration  of  the  preglacial  topography  by 
the  sub-Aftonian  drift. 

3.  The  development  of  a  new  topography  in  which  only  the  main 
lines  were  affected  by  the  larger  of  the  preglacial  valleys,  accounting 
for  the  peculiar  course  especially  of  South  River.     The  topography 
thus  developed  to  at  least  maturity  is  the  present  one  in  all  its  major 
details  (early  Aftonian). 

4.  A  partial  silting-up  of  valleys  by  material  washed  from  the  hills, 
the  sand  along  the  rivers,  now  overlain  by  recent  deposition,  forming 
the  basis  of  the  low  river  terrace  (late  Aftonian). 

5.  The  at  least  partial  mantling  of  the  late  Aftonian  topography 
by  drift  (Kansan)  that  obliterated  the  minor  details  of  the  late  Aftonian 
topography  but  did  not  obliterate  the  major  details. 

6.  The  working-over  of  material  on  the  surface  of  the  Kansan,  and 
of  other  material  exposed,  as  erosion  proceeded,  accompanied  by  consider- 
able deposition  of  loess,  all  of  which  has  continued  to  the  present,  though 
under  varying  conditions. 

7.  Renewed  erosion  and  waste  of  upland  following  changes  brought 
about  by  man. 

It  should  be  observed  that  this  history  is  of  a  region  outside  of  that 
occupied.by  any  of  the  post-Kansan  sheets  of  drift,  and  of  a  region  where 
drainage  outlined  as  above  stated  in  Aftonian  time  protected  the  county 
from  wash  from  melting  ice  later  than  Kansan  in  age. 


42 


APPENDIX 

The  construction  of  £  new  railroad  line  from  Des  Moines  to  Allerton 
(studied  in  1912)  has  given  a  series  of  excellent  exposures  through  the 
upland,  better  than  ever  before  available  in  this  portion  of  the  state. 
In  some  of  these  places  the  "gumbo'-'  presents  an  unbroken  sequence 
down  into  a  distinct  bowlder  bearing  Kansan  drift;  in  places  a  few  pebbles 
are  found  in  the  gumbo  even  up  to  two  inches  in  diameter,  though  such 
pebbles  are  extremely  rare;  and  in  places  there  is  washed  sand  and  gravel 
instead  of  gumbo.1  The  evidence  is  conclusive  that  this  deposit,  long 
known  as  the  gumbo  of  southwestern  Iowa,  is  an  upper  portion  of  the 
Kansan  drift  laid  down  in  the  closing  stages  of  the  Kansan  ice  invasion. 
In  accordance  with  this  discovery,  c,  d,  and  e,  pp.  7  and  37  should  be 
transferred  from  the  description  of  Post-Kansan  deposits  to  the  descrip- 
tion of  Kansan  Drift,  p.  30.  The  exposure  at  the  railroad  cut,  New 
Virginia,  and  at  Igo's  farm  (p.  15),  at  the  cemetery  (p.  26),  and  also 
that  illustrated  on  p.  25,  belong  to  this  same  horizon. 

1  John  L.  Tilton,  "A  New  Section  South  from  Des  Moines,  Iowa,"  Science,  1913; 
"A  'Pleistocene  Section  from  Des  Moines  to  Allerton,"  Proceedings  of  the  Iowa 
Academy  of  Science,  1913.  See  also  "Geology  of  Clarke  County,  Iowa,"  Iowa  Geo- 
logical Survey. 


1  n     7 

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